Hostname: page-component-745bb68f8f-f46jp Total loading time: 0 Render date: 2025-02-06T05:11:53.237Z Has data issue: false hasContentIssue false
  • English
  • Français

The rediscovery of malaria parasites of ungulates

Published online by Cambridge University Press:  22 July 2016

THOMAS J. TEMPLETON ,
ELLEN MARTINSEN ,
MORAKOT KAEWTHAMASORN  and
OSAMU KANEKO
THOMAS J. TEMPLETON
Affiliation:
Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan Department of Microbiology and Immunology, Weill Cornell Medical School, New York, New York 10021, USA
ELLEN MARTINSEN
Affiliation:
Center for Conservation and Evolutionary Genetics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20013-7012, USA
MORAKOT KAEWTHAMASORN
Affiliation:
The Veterinary Parasitology Unit, Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand
OSAMU KANEKO*
Affiliation:
Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
*
*Corresponding author: Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan. E-mail: okaneko@nagasaki-u.ac.jp
Rights & Permissions [Opens in a new window]

Summary

Over a hundred years since their first description in 1913, the sparsely described malaria parasites (genus Plasmodium) of ungulates have been rediscovered using molecular typing techniques. In the span of weeks, three studies have appeared describing the genetic characterization and phylogenetic analyses of malaria parasites from African antelope (Cephalophus spp.) and goat (Capra aegagrus hircus), Asian water buffalo (Bubalus bubalis), and North American white-tailed deer (Odocoileus virginianus). Here we unify the contributions from those studies with the literature on pre-molecular characterizations of ungulate malaria parasites, which are largely based on surveys of Giemsa-reagent stained blood smears. We present a phylogenetic tree generated from all available ungulate malaria parasite sequence data, and show that parasites from African duiker antelope and goat, Asian water buffalo and New World white-tailed deer group together in a clade, which branches early in Plasmodium evolution. Anopheline mosquitoes appear to be the dominant, if not sole vectors for parasite transmission. We pose questions for future phylogenetic studies, and discuss topics that we hope will spur further molecular and cellular studies of ungulate malaria parasites.

Keywords

malariaungulatesruminantsHaemosporidiaApicomplexamalaria parasites
Type
Review Article
Information
Parasitology , Volume 143 , Issue 12 , October 2016 , pp. 1501 - 1508
Check for updates
Copyright
Copyright © Cambridge University Press 2016 

INTRODUCTION

The first paper on ungulate malaria parasites begins off-handedly; ‘It would appear from a perusal of the available literature that malaria of antelopes has not hitherto been described…’, and proceeds to ‘place on record’ the description of a Plasmodium found in the blood of a captive common duiker antelope (Sylvicapra grimmia) in Malawi (Bruce et al. Reference Bruce, Harvey, Hamerton and Bruce1913). The word malaria was used because the antelope had an acute attack lasting 4 days, perhaps due to the stress of its captivity, and the parasite was described as Plasmodium based upon the morphological similarity of its intraerythrocytic stages to the human malaria parasite Plasmodium malariae. This same research team found another Plasmodium species in the common duiker (Bruce et al. Reference Bruce, Harvey, Hammerton, Davey and Bruce1915) but the organism was not revisited and named for another 50 years (Garnham, Reference Garnham1966; Keymer, Reference Keymer1966). In the ensuing years after 1913 additional ungulate Plasmodium parasites were described; in water buffalo (Bubalus bubalis) in India (Sheather, Reference Sheather1919), mouse deer (family Tragulidae) in Malaysia (Garnham and Edeson, Reference Garnham and Edeson1962; Sandosham et al. Reference Sandosham, Eyles, Wharton, Warren and Hoo1962), African marshbuck (Tragelaphus spekii) (van den Berghe, Reference van den Berghe1937) and domestic goats (Capra aegagrus hircus) in Africa (de Mello and Paes, Reference de Mello and Paes1923). A compendium of the parasites and studies are presented in Table 1 and the global distribution of malaria parasites of ungulate hosts is shown in Fig. 1. The parasites were typically identified in the course of blood surveys of parasites of wild and splenectomized animals, as well as veterinary diagnoses of likely immunocompromised water buffalo used in the production of rinderpest immune sera (Rao, Reference Rao1938; Riaz-ul-Hassan, Reference Riaz-ul-Hassan1953; Shastri et al. Reference Shastri, Shastri and Deshpande1985; Kolte et al. Reference Kolte, Maske and Tekade2002; Shinde et al. Reference Shinde, Maske, Samradhni, Kolte and Banubakode2005). The most recent identification of a new species of Plasmodium in ungulates was by P.C.C. Garnham, which included the description of an infection of a single splenectomized white-tailed deer in North America from a study in 1967 (Kuttler et al. Reference Kuttler, Robinson and Rogers1967; Garnham and Kuttler, Reference Garnham and Kuttler1980).

Fig. 1. Global distribution of the described ungulate malaria parasites (genus Plasmodium). Host animals include: (A) white-tailed deer, (B) water buffalo, (C) mouse deer, (D) domestic goat, (E) African marshbuck and (F) duiker antelope (Sylvicapra and Cephalophus spp.). Parasite species are listed below their respective hosts. Red shading indicates molecular typing of the malaria parasites (Boundenga et al. Reference Boundenga, Makanga, Ollomo, Gilabert, Rougeron, Mve-Ondo, Arnathau, Durand, Moukodoum, Okouga, Delicat-Loembet, Yacka-Mouele, Rahola, Leroy, Ba, Renaud, Prugnolle and Paupy2016; Martinsen et al. Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016; Templeton et al. Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016).

Table 1. The ungulate Plasmodium and Hepatocystis species including host species, geographic region, DNA markers associated with these taxa and references

In the past three decades the academic conversation on ungulate malaria parasites effectively ceased, with the exception of veterinary reports on water buffalo malaria (Shastri et al. Reference Shastri, Shastri and Deshpande1985; Kolte et al. Reference Kolte, Maske and Tekade2002; Shinde et al. Reference Shinde, Maske, Samradhni, Kolte and Banubakode2005); and the advent of molecular and cellular research on malaria parasites did not extend to include ungulate Plasmodium parasites but rather focused on the parasites of humans, non-human primates, rodents, reptiles and birds. Phylogenetic descriptions of Plasmodium and other Haemosporidia also ignored ungulate malaria parasites. This year, however, in the space of a few weeks, three studies have appeared describing the isolation of molecular markers for African, Asian and North American ungulates (Boundenga et al. Reference Boundenga, Makanga, Ollomo, Gilabert, Rougeron, Mve-Ondo, Arnathau, Durand, Moukodoum, Okouga, Delicat-Loembet, Yacka-Mouele, Rahola, Leroy, Ba, Renaud, Prugnolle and Paupy2016; Martinsen et al. Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016; Templeton et al. Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016). This review attempts to put these studies in context, reveal the importance of ungulates in the evolution of the malaria parasites, and aims to help reignite interest in a forgotten corner of malaria parasite research.

THREE INDEPENDENT STUDIES YIELD MOLECULAR DESCRIPTIONS OF UNGULATE MALARIA PARASITES

Many malaria researchers will have learned of ungulate malaria parasites while delving into Garnham's classic reference work from 1966, Malaria Parasites and Other Haemosporidia (Garnham, Reference Garnham1966). That memory, and the opportunity to study Giemsa-reagent stained slides of Plasmodium bubalis from a sick water buffalo from Thailand, inspired the screening of a wide inventory of ungulate blood DNA samples using a polymerase chain reaction (PCR) assay and Plasmodium-specific cytb primers, revealing the presence of malaria parasites from both water buffalo and African goats (Templeton et al. Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016). Independently, Plasmodium parasites of white-tailed deer in eastern North America were described in research led by Ellen Martinsen (Martinsen et al. Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016) following the serendipitous observation of a novel Plasmodium parasite cytb sequence in the course of a survey of mosquito vectors of avian malaria parasites. They then typed the vertebrate source of the mosquito blood meal by diagnostic PCR, which led them to the white-tailed deer (Odocoileus virginianus). Further PCR-based screening of white-tailed deer from across its range revealed the common and widespread nature of malaria parasites from white-tailed deer. The third study similarly noted a new Plasmodium cytb sequence, in this case through a survey of white-nosed monkey (Cercopithecus nictitans) bush-meat in Gabon (Ayouba et al. Reference Ayouba, Mouacha, Learn, Mpoudi-Ngole, Rayner, Sharp, Hahn, Delaporte and Peeters2012). On the supposition that the monkey was an accidental host, the researchers extended the survey to include bush-meat from other species, and thus identified a diversity of malaria parasite sequences from four duiker antelope species (genus Cephalophus) (Boundenga et al. Reference Boundenga, Makanga, Ollomo, Gilabert, Rougeron, Mve-Ondo, Arnathau, Durand, Moukodoum, Okouga, Delicat-Loembet, Yacka-Mouele, Rahola, Leroy, Ba, Renaud, Prugnolle and Paupy2016). We hope that the above three surveys are just the beginning of a reawakening of molecular and cellular research on ungulate Haemosporidia.

MOLECULAR-BASED INSIGHTS INTO UNGULATE PLASMODIUM EVOLUTION AND DIVERSITY

The three studies utilized molecular markers to generate phylogenetic trees, which uniformly placed ungulate malaria parasites as a clade closely related to but distinct from other mammalian Plasmodium (Boundenga et al. Reference Boundenga, Makanga, Ollomo, Gilabert, Rougeron, Mve-Ondo, Arnathau, Durand, Moukodoum, Okouga, Delicat-Loembet, Yacka-Mouele, Rahola, Leroy, Ba, Renaud, Prugnolle and Paupy2016; Martinsen et al. Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016; Templeton et al. Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016). Here we combine these newly available ungulate malaria parasite sequences to construct a new tree (Fig. 2), which includes sequence data from the mitochondrial cytochrome b (cytb) and cytochrome oxidase I (coxI) genes and the plastid caseinolytic protease gene (clpc) (Boundenga et al. Reference Boundenga, Makanga, Ollomo, Gilabert, Rougeron, Mve-Ondo, Arnathau, Durand, Moukodoum, Okouga, Delicat-Loembet, Yacka-Mouele, Rahola, Leroy, Ba, Renaud, Prugnolle and Paupy2016; Martinsen et al. Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016; Templeton et al. Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016). Phylogenies and nodal support values were estimated by Bayesian and Maximum Likelihood methods per Martinsen et al. (Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016). Malaria parasites infecting Asian water buffalo, African duiker antelope and domestic goat and North American white-tailed deer group together within a single clade, with the duiker and water buffalo parasites interspersed amongst each other indicative of multiple colonization events of these host species. The diversity of Plasmodium parasites revealed from these three studies is greater than the number of morphological species traditionally described by morphology from these ungulate host species. For example, we now know by molecular analysis of sequence data that two Plasmodium species infect water buffalo (Fig. 2B), but only one parasite, P. bubalis, is described in the literature. Ungulate malaria parasite diversity is likely to increase with further surveys, making it difficult if not impossible to assign molecular sequences with historical species names. The situation will become further muddied if the parasites are found to be promiscuous with respect to ungulate hosts.

Fig. 2. Unification of ungulate malaria parasites within a single clade. (A) We inferred a new tree for Haemosporidia using the mitochondrial cytochrome b (cytb) and cytochrome oxidase I (coxI) genes and the plastid caseinolytic protease (clpc) gene sequences; plus cytb sequences from duiker samples. Phylogenies and nodal support values were estimated by Bayesian and Maximum Likelihood methods as in Martinsen et al. (Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016). The ungulate malaria parasites group within a single clade, shown in red, which branches early in haemosporidian evolution. The clade is expanded in (B) to show the relationships between the ungulate malaria parasites. The Bayesian posterior probability and Maximum Likelihood bootstrap support values for this clade were 1.00 and 100% respectively. The grouping of the white-nosed monkey sample within this clade is discussed further in references Boundenga et al. (Reference Boundenga, Makanga, Ollomo, Gilabert, Rougeron, Mve-Ondo, Arnathau, Durand, Moukodoum, Okouga, Delicat-Loembet, Yacka-Mouele, Rahola, Leroy, Ba, Renaud, Prugnolle and Paupy2016) and Templeton et al. (Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016).

MOSQUITOES ARE THE LIKELY VECTORS OF UNGULATE MALARIA PARASITES

Ungulate malaria parasites thus far group within a single clade, suggesting that fundamental aspects of their natural histories might be conserved, such as their use of a specific arthropod transmission vector. Studies on anopheline mosquitoes feeding on water buffalo and mouse deer (Toumanoff, Reference Toumanoff1939; Wharton et al. Reference Wharton, Eyles, Warren, Moorhouse and Sandosham1963) proposed that they are the definitive host of ungulate Plasmodium. Mansonia crassipes was reported as a vector for the mouse deer malaria parasite, Plasmodium traguli (Warren et al. Reference Warren, Bennett and Cheong1964), in addition to Anopheles umbrosus (Wharton et al. Reference Wharton, Eyles, Warren, Moorhouse and Sandosham1963). Two of the recent molecular studies included mosquito surveys, and both implicated Anopheles spp. in the transmission of ungulate malaria parasites; Anopheles punctipennis in the case of the white-tailed deer parasites, and various Anopheles spp. collected from Gabonese forests regarding parasites infecting duiker antelope species (Boundenga et al. Reference Boundenga, Makanga, Ollomo, Gilabert, Rougeron, Mve-Ondo, Arnathau, Durand, Moukodoum, Okouga, Delicat-Loembet, Yacka-Mouele, Rahola, Leroy, Ba, Renaud, Prugnolle and Paupy2016; Martinsen et al. Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016). Further surveys of wild caught mosquitoes, and establishment of experimental feeding assays on infected animals using a variety of mosquitoes and other biting insects, will confirm these observations. Below, these points are reiterated with respect to the ungulate Hepatocystis parasites.

PRE-ERYTHROCYTIC AND ERYTHROCYTIC STAGES OF UNGULATE MALARIA PARASITES

Because ungulate malaria parasites branched prior to the clade containing avian, reptile and the other mammalian Plasmodium, it is of interest to understand the host tissues that support pre-erythrocytic development. For example, the sporozoites of avian malaria parasites develop within the cells of various tissues prior to the establishment of the erythrocytic cycle (Valkiūnas, Reference Valkiūnas2005), in contrast to the pre-erythrocytic development within hepatocytes of all characterized mammalian malaria parasites, including mouse deer Plasmodium (Garnham and Edeson, Reference Garnham and Edeson1962; Sandosham et al. Reference Sandosham, Eyles, Wharton, Warren and Hoo1962). Knowledge is lacking on the complete life cycle of ungulate malaria parasites within their vertebrate hosts. It also has not been determined if ungulate malaria parasites have hypnozoite stages. This is relevant to the Plasmodium of white-tailed deer, as mosquitoes are absent for much of the year, and the parasite must either persist in its vertebrate host through a chronic blood stage infection or recrudesce via activation of latent hypnozoites.

The parasites of ungulates appear to share the life history trait of extremely low or sub-microscopic blood parasitaemias, persisting as chronic, occult infections in the blood of their ungulate hosts. Schizonts are frequently so scarce that distinguishing Hepatocystis vs Plasmodium blood stage infections is difficult (Keymer, Reference Keymer1966). As with the original species description of P. odocoilei from a single white-tailed deer, Martinsen et al. (Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016) documented extremely low blood parasitaemia and oftentimes undetectable levels of the malaria parasites of this host species by visualization of blood smears from positive animals sampled during warm months. This likely explains why P. odocoilei defied all attempts at rediscovery for decades despite a multitude of white-tailed deer blood parasite studies by light microscopy methods. The occult or subpatent status of the parasite might be punctuated by elevated parasite blood burdens and gametocytaemia for the facilitation of transmission during the mosquito season. Alternatively, the parasite may maintain infectivity at sub-microscopic levels of parasitaemia, as has been shown for malaria parasites in humans (reviewed in Okell et al. Reference Okell, Ghani, Lyons and Drakeley2009) and for many other mammalian malaria parasites including the two species of common duiker Plasmodium (Garnham, Reference Garnham1966). The duiker parasites, Plasmodium cephalophi and Plasmodium brucei, likewise resisted efforts at their rediscovery for over 50 years due to their light parasitaemia, until researchers splenectomized duikers to recover the parasites (Keymer, Reference Keymer1966). Plasmodium bubalis also appears to be occult; for example, in a PCR cytb survey of 144 blood samples from water buffalo in the Mukdahan Province of Thailand, 45% were positive for Plasmodium, but only one of these samples yielded microscopic detection of the parasite in Giemsa reagent-stained blood smears (Templeton et al. Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016). The occult nature of the blood stages of ungulate malaria parasites emphasizes the need for molecular-based methods in the discovery and rediscovery of the malaria parasites of ungulates.

Descriptions of Giemsa reagent-stained blood smears of ungulate malaria parasites indicate that great diversity exists within the clade with respect to morphologies of the intraerythrocytic stages. For example, P. bubalis parasites possess long, bar-shaped hemozoin crystals (Sheather, Reference Sheather1919; Templeton et al. Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016), also observed in P. cephalophi (Keymer, Reference Keymer1966), whereas the granules are small in P. odocoilei (Garnham and Kuttler, Reference Garnham and Kuttler1980; Martinsen et al. Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016). The latter parasite shares with P. cephalophi profound enlargement of the host erythrocyte, and spiked processes on the host erythrocyte, which Garnham noted are reminiscent of similar structures which provide the Latin name for the bat haemosporidian, Nycteria medusiformis (Garnham and Kuttler, Reference Garnham and Kuttler1980). Plasmodium odocoilei also imparts a pink discoloration and the accumulation of large vacuoles within the erythrocyte (Garnham and Kuttler, Reference Garnham and Kuttler1980).

THE PARAPHYLETIC NATURE OF HAEMOSPORIDIA AND QUESTIONS REGARDING UNGULATE PLASMODIUM

The Plasmodium clade within Haemosporidia is paraphyletic, in that it includes the bat malaria parasites Nycteria and Hepatocystis (Escalante et al. Reference Escalante, Freeland, Collins and Lal1998; Perkins and Schall, Reference Perkins and Schall2002; Martinsen et al. Reference Martinsen, Perkins and Schall2008; Witsenburg et al. Reference Witsenburg, Salamin and Christe2012; Schaer et al. Reference Schaer, Perkins, Decher, Leendertz, Fahr, Weber and Matuschewski2013; Borner et al. Reference Borner, Pick, Thiede, Kolawole, Kingsley, Schulze, Cottontail, Wellinghausen, Schmidt-Chanasit, Bruchhaus and Burmester2016; Templeton et al. Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016). In contrast to Plasmodium these parasites do not possess the capacity for intraerythrocytic schizogony, and are vectored by biting flies rather than mosquitoes. The three recent studies of ungulate malaria parasites present phylogenetic trees, which differ in the placement of ungulate malaria parasites within Haemosporidia, and their relationship with Polychromophilus, another haemosporidian parasite of bats (Fig. 3). Thus it formally remains a question if ungulates represent the basal branch of Haemosporidia in mammals, with the avian parasites such as Haemoproteus, Parahaemoproteus and Leucocytozoon representing the root of the Haemosporidia. All three studies support a close relationship of ungulate malaria parasites to Polychromophilus, which lacks erythrocyte schizogony, has merogony in Kupffer and endothelial cells of multiple tissues, and is vectored by bat flies of the family Nycteribiidae. More robust sampling of DNA markers from Polychromophilus spp., as well as other haemosporidian groups including the ungulate malaria parasites, will aid in obtaining higher resolution trees to resolve the base of the Haemosporidia.

Fig. 3. The paraphyletic nature of Haemosporidia and the relationship of ungulate malaria parasites to Polychromophilus. Plasmodium species are in black font, and other genera in red font. (A) Topology from Martinsen et al. (Reference Martinsen, McInerney, Brightman, Ferebee, Walsh, McShea, Forrester, Ware, Joyner, Perkins, Latch, Yabsley, Schall and Fleischer2016). (B) Topology from Templeton et al. (Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016), in which the relationship of ungulate Plasmodium and Polychromophilus was not well-resolved (indicated by a blue box). In other trees inferred from whole mtDNA sequences, which did not include Polychromophilus (Templeton et al. Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016) the bird and lizard Plasmodium species grouped within a single well-supported clade (indicated by a green box).

UNGULATE HEPATOCYSTIS PARASITES REMAIN UNCHARACTERIZED

An ungulate Hepatocystis parasite, Hepatocystis hippopotami, has been described in the hippopotamus (Garnham, Reference Garnham1958) and two species, Hepatocystis fieldi and Hepatocystis fieldi ceylonensis, in the mouse deer (Garnham and Edeson, Reference Garnham and Edeson1962; Sandosham et al. Reference Sandosham, Eyles, Wharton, Warren and Hoo1962; Dissanaike, Reference Dissanaike1963). They differ from ungulate Plasmodium in the observation of merocysts on the surface of the liver and the absence of intraerythrocytic schizogony. Mouse deer have been observed carrying both Hepatocystis and Plasmodium (P. traguli) infections, which can be differentiated based upon gametocyte morphology (Dissanaike, Reference Dissanaike1963). Thus the puzzle of ungulate Haemosporidia parasites has an unsolved component – the molecular phylogenetic placement of ungulate Hepatocystis. The Asian mouse deer might be the best source of parasite material with which to pursue research on this topic, as infections were reported to be more common than those of the hippopotamus. It is of interest to determine if ungulate Hepatocystis and Plasmodium diverged from a common ungulate parasite ancestor, or if they are the descendants of independent host-switches to ungulates. Related to this, the insect vector of ungulate Hepatocystis also has not been described; its identity, coupled with the phylogenetic placement of the Hepatocystis, might indicate if there was also host switch in the vector.

THE VALUE OF UNGULATE PLASMODIUM FOR GENOME STUDIES

Whole genome sequence information is invaluable in the study of the evolution of malaria parasites. For example, understanding the origin and diversification of parasite-encoded proteins, which mediate host interactions, such as the Plasmodium-encoded erythrocyte surface receptors PfEMP1, PIR and SURFIN, would be greatly informed by the genome sequences of avian and ungulate Plasmodium. The recent completion of genome sequence for Haemoproteus tartakovskyi (Bensch et al. Reference Bensch, Canbäck, DeBarry, Johansson, Hellgren, Kissinger, Palinauskas, Videvall and Valkiūnas2016) will be valuable in describing the evolution of Haemosporidia virulence genes. Similarly, ungulate malaria parasites are of interest for genome projects because of their distant relationship to other mammalian parasites. The low parasitaemias common to these parasites is challenging in terms of preparing quantities of DNA sufficient for whole genome sequencing, but might be overcome by infection of splenectomized animals, through in vitro culture, or via selective whole genome amplification (Sundararaman et al. Reference Sundararaman, Plenderleith, Liu, Loy, Learn, Li, Shaw, Ayouba, Peeters, Speede, Shaw, Bushman, Brisson, Rayner, Sharp and Hahn2016). The goat malaria parasite, P. caprae, might be useful because of the availability of goats, which are easy to splenectomize, and to restrain for bloodletting. Bovinized splenectomized SCID mice, in which the mouse blood component is replaced by frequent intraperitoneal injections of bovine blood, might also allow sufficient production of ungulate Plasmodium for genome studies. This system has been successfully used to propagate Babesia parasites (Arai et al. Reference Arai, Tsuji, Kim, Nakada, Kirisawa, Ohta and Ishihara1998). Tissue culture adaptation might also be attempted with either P. caprae or P. bubalis, since blood draws of large volumes are possible from both host animals. Recent advances in whole genome sequencing have greatly lowered the cost, and requirements for abundance and purity of starting material; and it is anticipated that these methods will benefit the sequencing of the above challenging parasites. Whole genome amplification methods (for example, see Oyola et al. Reference Oyola, Manske, Campino, Claessens, Hamilton, Kekre, Drury, Mead, Gu, Miles, MacInnis, Newbold, Berriman and Kwiatkowski2014) might also allow whole or high coverage genomes for annotation of virulence genes and sequences for phylogenetic analyses.

VETERINARY AND WILDLIFE MANAGEMENT ASPECTS OF UNGULATE MALARIA PARASITES

The world population of water buffalo was approximately 200 million head in 2014, with over 95% located in Asia, according to databases at the Food and Agriculture Organization (FAO) of the United Nations (http://faostat3.fao.org). Water buffalo can be subdivided into 2 subspecies: river buffalo, constituting approximately 70% of the population, and swamp buffalo. The population of goats was over one billion head in 2014 and distributed worldwide. Together water buffalo and goat contribute a significant share of global milk; and in several countries are the major milk and meat producing animals. Successful infrastructure development projects across Asia have resulted in considerable shipping of water buffalo both within and across borders. The livestock frequently spend long periods of time in transport and quarantine, and are intermixed with local stock. Consequently, any pathogens that compromise food production, whether they be of bacterial, viral or protozoan nature, are threats to both local economies and international food security (Godfray et al. Reference Godfray, Beddington, Crute, Haddad, Lawrence, Muir, Pretty, Robinson, Thomas and Toulmin2010).

Templeton et al. (Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016) reported that Plasmodium is widespread in water buffalo of the Mukdahan Province of Thailand, with up to 48% prevalence using a sensitive Plasmodium-specific PCR assay. They also observed one case of mortality of a malarial buffalo, although it was not determined if the malaria parasite was an opportunistic infection and not the causative agent of mortality. Malaria has been observed in likely immunocompromised water buffalo used in the production of rinderpest and anthrax immune sera, including deaths possibly attributed to the parasite (Rao, Reference Rao1938; Riaz-ul-Hassan, Reference Riaz-ul-Hassan1953; Shastri et al. Reference Shastri, Shastri and Deshpande1985; Kolte et al. Reference Kolte, Maske and Tekade2002; Shinde et al. Reference Shinde, Maske, Samradhni, Kolte and Banubakode2005). Although we feel that it is unnecessary at this time to raise public concern regarding water buffalo malaria parasites, it is important to develop rapid diagnostic tests (RDT) for research purposes, and to formulate epidemiological questions to be addressed by field surveys using RDT and PCR. Diagnostic assays might be employed in veterinary cases that have unknown causes or suspected involvement of malaria parasites. Templeton et al. (Reference Templeton, Asada, Jiratanh, Ishikawa, Tiawsirisup, Sivakumar, Namangala, Takeda, Mohkaew, Ngamjituea, Inoue, Sugimoto, Inagaki, Suzuki, Yokoyama, Kaewthamasorn and Kaneko2016) reported screening of 53 samples of goat blood for Plasmodium, from Zambia, and identified a single positive sample. In a screen of 46 goat samples from Vietnam positive samples were not identified. These assays did not contain positive controls for DNA quality, since we were looking for positive samples rather than an epidemiological survey. To our knowledge malaria parasites have not been described in cows (Bos taurus). In a screen of 140 samples from Vietnam we did not identify Plasmodium-positive samples. Thus it is necessary to extend such surveys to include more goats and cows, globally, in order to determine the distribution and prevalence of malaria parasites in these domestic ruminants. It is also of interest to develop and include malaria diagnostics as a veterinary consideration for undiagnosed ailments in goats, and in cows if surveys identify Plasmodium parasites. In summary, the global health and economic burden of malaria parasite infections in ungulate hosts of domestic, such as water buffalo and goat, and wild, such as white-tailed deer and duiker antelope species, are unknown but future study will be aided by the further development of molecular markers and the formulation of topics and questions for study.

ACKNOWLEDGEMENTS

Richard Culleton is thanked for many thoughtful discussions and critical reading of the manuscript.

FINANCIAL SUPPORT

T. J. T. was supported by a visiting professorship at the Institute of Tropical Medicine, Nagasaki University, Japan. This work was conducted at the Joint Usage/Research Center on Tropical Disease, Institute of Tropical Medicine, Nagasaki University and supported in part by Grants-in-Aids for Scientific Research JP16H05807 and Scientific Research on Innovative Areas JP23117008, MEXT, Japan (O.K.). M. K. is a recipient of grants for development of new faculty staff, Chulalongkorn University (GDNS 56-020-31-001) and Chulalongkorn University-Veterinary Science Research Fund (RG 15/2559). The white-tailed deer work was carried out at the Smithsonian Conservation Biology Institute's Center for Conservation and Evolutionary Genetics and funded by a grant from the Morris Animal Foundation (D10ZO-043) and the National Science Foundation (DEB-1241041). We thank Robert C. Fleischer for providing resources and input into the white-tailed deer malaria parasite portion of the work.

References

REFERENCES

Arai, S., Tsuji, M., Kim, S. J., Nakada, K., Kirisawa, R., Ohta, M. and Ishihara, C. (1998). Antigenic and genetic diversities of Babesia ovata in persistently infected cattle. Journal of Veterinary Medicine and Science 60, 1321–1327.CrossRefGoogle ScholarPubMed
Ayouba, A., Mouacha, F., Learn, G. H., Mpoudi-Ngole, E., Rayner, J. C., Sharp, P. M., Hahn, B. H., Delaporte, E. and Peeters, M. (2012). Ubiquitous Hepatocystis infections, but no evidence of Plasmodium falciparum-like malaria parasites in wild greater spot-nosed monkeys (Cercopithecus nictitans). International Journal of Parasitology 42, 709–713.CrossRefGoogle ScholarPubMed
Bensch, S., Canbäck, B., DeBarry, J. D., Johansson, T., Hellgren, O., Kissinger, J. C., Palinauskas, V., Videvall, E. and Valkiūnas, G. (2016). The genome of Haemoproteus tartakovskyi and its relationship to human malaria parasites. Genome Biology and Evolution 8, 1361–1373.CrossRefGoogle ScholarPubMed
Borner, J., Pick, C., Thiede, J., Kolawole, O. M., Kingsley, M. T., Schulze, J., Cottontail, V. M., Wellinghausen, N., Schmidt-Chanasit, J., Bruchhaus, I. and Burmester, T. (2016). Phylogeny of haemosporidium blood parasites revealed by a multi-gene approach. Molecular Phylogenetics and Evolution 94, 221–231.CrossRefGoogle ScholarPubMed
Boundenga, L., Makanga, B., Ollomo, B., Gilabert, A., Rougeron, V., Mve-Ondo, B., Arnathau, C., Durand, P., Moukodoum, N. D., Okouga, A. P., Delicat-Loembet, L., Yacka-Mouele, L., Rahola, N., Leroy, E., Ba, C. T., Renaud, F., Prugnolle, F. and Paupy, C. (2016). Haemosporidian parasites of antelopes and other vertebrates from Gabon, Central Africa. PLoS ONE 11, e0148958.CrossRefGoogle ScholarPubMed
Bruce, D., Harvey, D., Hamerton, A. E. and Bruce, L. (1913). Plasmodium cephalophi sp. nov . Proceedings of the Royal Society B 87, 45–47.Google Scholar
Bruce, D., Harvey, D., Hammerton, A. E., Davey, J. B. and Bruce, L. (1915). Trypanosomes and other parasites of animals in Nyasaland. Reports of the Sleeping Sickness Commission of the Royal Society 16, 203–208.Google Scholar
de Mello, F. and Paes, S. (1923). Sur une plasmodie du sang des chèvres. Comptes Rendus des Séances de la Société de Biologie 88, 829–830.Google Scholar
Dissanaike, A. S. (1963). On some blood parasites of wild animals in Ceylon. Ceylon Veterinary Journal 11, 73–86.Google Scholar
Escalante, A. A., Freeland, D. E., Collins, W. E. and Lal, A. A. (1998). The evolution of primate malaria parasites based on the gene encoding cytochrome b from the linear mitochondrial genome. Proceedings of the National Academy of Sciences of the United States of America 95, 8124–8129.CrossRefGoogle ScholarPubMed
Garnham, P. C. C. (1958). A malaria parasite of the hippopotamus. Journal of Protozoology 5, 149–151.CrossRefGoogle Scholar
Garnham, P. C. C. (1966). Malaria Parasites and other Haemosporidia. Blackwell Sci. Pub., Oxford.Google Scholar
Garnham, P. C. C. and Edeson, J. F. B. (1962). Two new malaria parasites of the Malayan mouse deer. Rivista di Malariologia 41, 1–8.Google Scholar
Garnham, P. C. C. and Kuttler, K. L. (1980). A malaria parasite of the white-tailed deer (Odocoileus virginianus) and its relation with known species of Plasmodium in other ungulates. Proceedings of the Royal Society of London B Biological Sciences 206, 395–402.Google ScholarPubMed
Godfray, H. C., Beddington, J. R., Crute, I. R., Haddad, L., Lawrence, D., Muir, J. F., Pretty, J., Robinson, S., Thomas, S. M. and Toulmin, C. (2010). Food security: the challenge of feeding 9 billion people. Science 327, 812–818.CrossRefGoogle ScholarPubMed
Keymer, I. F. (1966). Studies on Plasmodium (Vinckeia) cephalophi of the grey duiker (Sylvicapra grimmia). Annals of Tropical Medicine and Parasitology 60, 129–138.CrossRefGoogle ScholarPubMed
Keymer, I. F. (1969). Investigations on the duiker (Sylvicapra grimmia) and its blood protozoa in Central Africa. Philosophical Transactions of the Royal Society of London B Biological Sciences 255, 33–108.Google Scholar
Kolte, S. W., Maske, D. K. and Tekade, S. R. (2002). A note on occurrence of Plasmodium bubalis in buffaloes (Bubalus bubalis) at Nagpur. Journal of Veterinary Parasitology 16, 193.Google Scholar
Kuttler, K. L., Robinson, R. M. and Rogers, W. P. (1967). Exacerbation of latent erythrocytic infections in deer following splenectomy. Canadian Journal of Comparative Medicine and Veterinary Science 31, 317–319.Google ScholarPubMed
Martinsen, E. S., Perkins, S. L. and Schall, J. J. (2008). A three-genome phylogeny of malaria parasites (Plasmodium and closely related genera): evolution of life-history traits and host switches. Molecular Phylogenetics and Evolution 47, 261–273.CrossRefGoogle ScholarPubMed
Martinsen, E. S., McInerney, N., Brightman, H., Ferebee, K., Walsh, T., McShea, W. J., Forrester, T. D., Ware, L., Joyner, P. H., Perkins, S. L., Latch, E. K., Yabsley, M. J., Schall, J. J. and Fleischer, R. C. (2016). Hidden in plain sight: Cryptic and endemic malaria parasites in North American white-tailed deer (Odocoileus virginianus). Science Advances 2, e1501486.CrossRefGoogle ScholarPubMed
Okell, L. C., Ghani, A. C., Lyons, E. and Drakeley, C. J. (2009). Submicroscopic infection in Plasmodium falciparum-endemic populations: a systematic review and meta-analysis. Journal of Infectious Disease 200, 1509–1517.CrossRefGoogle ScholarPubMed
Oyola, S. O., Manske, M., Campino, S., Claessens, A., Hamilton, W. L., Kekre, M., Drury, E., Mead, D., Gu, Y., Miles, A., MacInnis, B., Newbold, C., Berriman, M. and Kwiatkowski, D. P. (2014). Optimized whole-genome amplification strategy for extremely AT-biased template. DNA Research 21, 661–671.CrossRefGoogle ScholarPubMed
Perkins, S. L. and Schall, J. J. (2002). A molecular phylogeny of malarial parasites recovered from cytochrome b gene sequences. Journal of Parasitology 88, 972–978.CrossRefGoogle ScholarPubMed
Rao, M. A. N. (1938). A note on Plasmodium bubalis Sheather, 1919. Indian Journal of Veterinary Science and Animal Husbandry 8, 387–389.Google Scholar
Riaz-ul-Hassan, S. (1953). Further observations on malaria in buffaloes. Pakistan Journal of Health 3, 59–63.Google ScholarPubMed
Sandosham, A. A., Eyles, D. E., Wharton, R. G., Warren, M. and Hoo, C. C. (1962). Plasmodium sp. and Hepatocystis sp. in the mouse-deer (Tragulus javanicus) in Malaya. The Medical Journal of Malaya 17, 78–90.Google Scholar
Schaer, J., Perkins, S. L., Decher, J., Leendertz, F. H., Fahr, J., Weber, N. and Matuschewski, K. (2013). High diversity of West African bat malaria parasites and a tight link with rodent Plasmodium taxa. Proceedings of the National Academy of Sciences of the United States of America 110, 17415–17419.CrossRefGoogle Scholar
Shastri, S. R., Shastri, U. V. and Deshpande, P. D. (1985). Haematozoan infections in buffalo, Bubalus bubalis, in Maharashtra. Indian Journal of Parasitology 9, 183–185.Google Scholar
Sheather, A. L. (1919). A malarial parasite in the blood of a buffalo. Journal of Comparative Pathology and Therapeutics 32, 223–229.CrossRefGoogle Scholar
Shinde, P. N., Maske, D. K., Samradhni, D., Kolte, S. W. and Banubakode, S. B. (2005). Some observations on bovine malaria associated with developing phases of Plasmodium bubalis in Vidarbha region of Maharashtra. Journal of Veterinary Parasitology 19, 61–62.Google Scholar
Sundararaman, S. A., Plenderleith, L. J., Liu, W., Loy, D. E., Learn, G. H., Li, Y., Shaw, K. S., Ayouba, A., Peeters, M., Speede, S., Shaw, G. M., Bushman, F. D., Brisson, D., Rayner, J. C., Sharp, P. M. and Hahn, B. H. (2016). Genomes of cryptic chimpanzee Plasmodium species reveal key evolutionary events leading to human malaria. Nature Communications 7, 11078.CrossRefGoogle ScholarPubMed
Templeton, T. J., Asada, M., Jiratanh, M., Ishikawa, S. A., Tiawsirisup, S., Sivakumar, T., Namangala, B., Takeda, M., Mohkaew, K., Ngamjituea, S., Inoue, N., Sugimoto, C., Inagaki, Y., Suzuki, Y., Yokoyama, N., Kaewthamasorn, M. and Kaneko, O. (2016). Ungulate malaria parasites. Scientific Reports 6, 23230.CrossRefGoogle ScholarPubMed
Toumanoff, C. (1939). Le paludisme des buffles peut-il fausser les indices oocystiques et sporozoitiques en Indochine? Bulletin de la Société de Pathologie Exotique et de ses Filiales 32, 80–87.Google Scholar
Valkiūnas, G. (2005). Avian Malaria Parasites and other Haemosporidia. CRC Press, Boca Raton, FL.Google Scholar
van den Berghe, L. (1937). Plasmodium limnotragi n. sp., d'une antilope Limnotragus spekei . Bulletin de la Société de Pathologie Exotique et de ses Filiales 30, 272–274.Google Scholar
Warren, M., Bennett, G. F., and Cheong, W. H. (1964). Natural plasmodial infections in Mansonia (Coquillettidia) crassipes . The Medical Journal of Malaya 19, 55.Google Scholar
Wharton, R. H., Eyles, D. E., Warren, M., Moorhouse, D. E. and Sandosham, A. A. (1963). Investigations leading to the identification of members of the Anopheles umbrosus group as the probable vectors of mouse deer malaria. Bulletin of the World Health Organization 29, 357–374.Google Scholar
Witsenburg, F., Salamin, N. and Christe, P. (2012). The evolutionary host switches of Polychromophilus: a multi-gene phylogeny of the bat malaria genus suggests a second invasion of mammals by a haemosporidian parasite. Malaria Journal 11, 53.CrossRefGoogle ScholarPubMed
Figure 0

Fig. 1. Global distribution of the described ungulate malaria parasites (genus Plasmodium). Host animals include: (A) white-tailed deer, (B) water buffalo, (C) mouse deer, (D) domestic goat, (E) African marshbuck and (F) duiker antelope (Sylvicapra and Cephalophus spp.). Parasite species are listed below their respective hosts. Red shading indicates molecular typing of the malaria parasites (Boundenga et al.2016; Martinsen et al.2016; Templeton et al.2016).

Figure 1

Table 1. The ungulate Plasmodium and Hepatocystis species including host species, geographic region, DNA markers associated with these taxa and references

Figure 2

Fig. 2. Unification of ungulate malaria parasites within a single clade. (A) We inferred a new tree for Haemosporidia using the mitochondrial cytochrome b (cytb) and cytochrome oxidase I (coxI) genes and the plastid caseinolytic protease (clpc) gene sequences; plus cytb sequences from duiker samples. Phylogenies and nodal support values were estimated by Bayesian and Maximum Likelihood methods as in Martinsen et al. (2016). The ungulate malaria parasites group within a single clade, shown in red, which branches early in haemosporidian evolution. The clade is expanded in (B) to show the relationships between the ungulate malaria parasites. The Bayesian posterior probability and Maximum Likelihood bootstrap support values for this clade were 1.00 and 100% respectively. The grouping of the white-nosed monkey sample within this clade is discussed further in references Boundenga et al. (2016) and Templeton et al. (2016).

Figure 3

Fig. 3. The paraphyletic nature of Haemosporidia and the relationship of ungulate malaria parasites to Polychromophilus. Plasmodium species are in black font, and other genera in red font. (A) Topology from Martinsen et al. (2016). (B) Topology from Templeton et al. (2016), in which the relationship of ungulate Plasmodium and Polychromophilus was not well-resolved (indicated by a blue box). In other trees inferred from whole mtDNA sequences, which did not include Polychromophilus (Templeton et al.2016) the bird and lizard Plasmodium species grouped within a single well-supported clade (indicated by a green box).