INTRODUCTION
ROBIN A.J. NICHOLAS
Mycoplasma Group, Animal Health and Veterinary Laboratories Agency (Weybridge), New Haw, Weybridge, UK
Mycoplasmas are members of the class Mollicutes, which comprises all the wall-less bacteria.
They are characterized by their small genome size (0.58—0.22 Mbp), a low G+C content (23—40 mol %) of the genome and a permanent lack of a cell wall. Over 200 species have so far been described and have been isolated from plant and both invertebrate and vertebrate animal hosts. Many more remain to be characterized. By far the majority are non- pathogenic, living on mucosal surfaces, where they remain reliant on the host for their nutritional requirements, being totally devoid of genes for biosynthetic processes. Some, however, can be invasive and cause serious diseases such as contagious bovine and caprine pleuropneumonia and atypical pneumonia in humans, one of the most common community acquired pneumonias worldwide. Generally the features of mycoplasma diseases in animals include respiratory signs, often accompanied by arthritis, mastitis and eye infections; infertility, abortions and nervous signs may also be seen.Mollicutes inhabit most animal wildlife species, including insects, fish, amphibians, reptiles, birds and mammals.
New species are being detected frequently in many animals such as desert tortoises, snakes, mink, crocodiles, birds of prey and sea mammals, where they are probably of little consequence under normal situations. However, mycoplasmas are notorious for exploiting stressful situations, including those caused by weather fluctuations, overcrowding and, probably linked to these, hormonal disturbances. It is likely that the majority of reported outbreaks of mycoplasmosis in wildlife species are associated with the unnatural conditions of captivity or semi-captivity found in zoos, wildlife parks and farms where animals are intensively reared. The conditions under which laboratory animals such as rabbits, rats and mice are bred is also conducive to horizontal spread of mycoplasmas like M.
pulmonis. This has implications both for the health of the laboratory animal, in which high morbidity and low fertility may be seen, and to the results of the experiments in which these animals are being used. In these circumstances, normally non-pathogenic strains can cause disease because of a depressed host immune system. More commonly, however, pathogenic species in one host species may have the opportunity to infect a different host species by close contact, a situation that would be unlikely to occur in the wild. Recent outbreaks of what was thought to be a highly host-specific disease, contagious caprine pleuropneumonia, in various gazelle species in a private collection on an island in the United Arab Emirates was linked to the introduction of goats(1). Even in the wild, food shortages brought about by seasonal changes may force wildlife to feed closer to domesticated species, as has been seen with the spread of infectious keratoconjunctivitis from sheep to the wild small ruminant species described in this chapter. The mycoplasma flora of captive animals may not be representative of animals in the wild but may have implications in the event of escape or reintroduction to the wild, a distinct possibility in many zoos and wildlife parks.Infectious Diseases of Wild Mammals and Birds in Europe, First Edition. Edited by Dolores Gavier-Widen, J. Paul Duff, and Anna Meredith. © 2012 Blackwell Publishing Ltd. Published 2012 by Blackwell Publishing Ltd. Material authored by Robin Nicholas remains Crown Copyright.