Adjectives can have an astonishing ability to refresh those nouns they describe. Take, for example, human African trypanosomiasis, the disease upon which I have worked for over 20 years. When I started it was merely a tropical disease. Much of the pioneering work had been performed by servants of the British, French and Belgian empires. Progress against trypanosomiasis waned as the Europeans abandoned their Imperial adventure. Diseases like HAT became resurgent. No-one appeared to care. Fortunately someone introduced the idea that these diseases could conveniently be classed as ‘neglected’. The re-classification worked. The World Health Organization now houses a department of Neglected Tropical Diseases, and one of the most successful of the public private partnerships that has arisen to deal with some of the world's health problems is the Drugs for Neglected Diseases initiative. A simple adjective allowed new impetus to be placed upon its control. And, in fact, the incidence of HAT has plummeted under its new classification.

Elsewhere we have witnessed an increased interest in ‘emerging’ infectious diseases too, i.e. diseases previously rare, or unknown, in man, whose incidence has started to increase in recent years, usually related to changes in demography as the world changes. Naveed Ahmed Khan has produced a text on Emerging Protozoan Pathogens. As with many books today, each chapter has its own author – which certainly facilitates writing a book, but inevitably leads to a lack of uniformity in style and rational cross-referencing between sections becomes difficult. The book is essentially divided into sections on amoeba (chapters each on Acanthamoeba, Balamuthia, Naegleria and Blastocystis), apicomplexans (Cryptosporidium, Toxoplasma, Isospora and Babesia), the ciliates (Balantidium) and flagellates (Giardia and Trichomonas). The editor must have had a little struggle in choosing which diseases could be considered as ‘emerging’. Certainly toxoplasmosis, a well-known pathogen for many years, offered some cause for thought. However, its increased incidence, and severity in the wake of the global HIV/Aids pandemic justifies its inclusion. Indeed, the emergence of many of the pathogens outlined here relates to the global rise in immunosuppression and it would have been interesting to have read a detailed account of HIV's impact on emerging infections. Other great changes that are widely perceived to impact on emerging infections, such as environmental change and agricultural practise also pass largely unconsidered. The general gluing together of the book, generally, left a little to be desired. For example, a basic description of protozoan biology and also their interaction with the host immune system came towards the end of the book, whereas such introductory material would have fitted more comfortably at the start.

Notwithstanding these minor quibbles, any fresh angle that helps reinvigorate our interest in, and understanding of, protozoan infections is to be welcome and Khan's book certainly fills a niche.