Diseases of lower vertebrates and biomedical research

Laboratory Animals (1977) 11, 119-123 119 Diseases of lower vertebrates and biomedical research JOHN E. COOPER Division of Comparative Medicine, Clinical Research Centre, Watford Road, Harrow, HAl 3 UJ Summary The historical and present role of lower (non- mammalian) vertebrates in biomedical research is discussed. Examples are given of disease problems and experimental studies. It is suggested that lower vertebrates may prove of increasing value in this field in the future. The author's definition of 'lower vertebrates' is somewhat broader than that used by zoologists. The term will be used to cover birds, reptiles, amphibians and fish-in other words, the non- mammalian vertebrates-whereas the conventional approach is to include birds with the mammals as 'higher' vertebrates. One does not need to dwell upon the significance of lower vertebrates as subjects for basic biological research. In the past they have played an important part in studies on anatomy, behaviour, ecology, genetics and evolution. The inclusion of so many lower vertebrates in UFAW (1972) is a pointer to their popularity as experimental species in this context. Lower vertebrates also have an important role to play in biomedical studies. Interest in their diseases is not new. An Egyptian painting dated 1450 BC depicts a tilapia fish with a grossly dis- tended abdomen, probably ascites (Mawdesley- Thomas, 1972), and an authoritative paper on the history of fish diseases refers to publications on the subject dated 330 BC (McGregor, 1963). Involve- ment in amphibian and reptile medicine is more recent but, as will be mentioned later, studies on avian disease in Britain alone extend back to the early days of printing, if not earlier. At the present time study of lower vertebrate disease can be considered under the headings: veterinary diagnosis and treatment; human health problems, especially zoonoses and environmental mon- itoring; development and use of animal models for disease; other experimental uses, e.g. disease diag- noses, toxicity tests and vaccine production and testing. The last pair will be discussed together as they cover those aspects of biomedical research which are most appropriate to this paper. Veterinary diagnosis and treatment This will not be discussed in detail in this paper. Suffice it to say that many hundreds of thousands of lower vertebrates, ranging from the goldfish to the budgerigar, are kept as pets in this and other countries and these regularly need veterinary atten- tion. Interest in diseases of birds is hardly new: the treatment of trained falcons was first discussed in an English printed book in the 15th century (Barnes, 1486). Many lower vertebrates are maintained in zoological and scientific establishments and, here again, disease control is essential. There are economic reasons for such work. For example, fish farming is becoming established as an important source of human food and with it disease problems are emerging. As a result interest in lower vertebrate disease has increased enormously and there are units both in Britain and overseas where postgraduate study on fish diseases is actively pursued. Another example of the economic justification for work on reptile diseases concerns commercial snake farms, usually situated in the tropics, where poisonous species are maintained and 'milked' for the venom. The author was responsible for health control at one such farm in Kenya in 1970-73 and, amongst other problems, investigated a septicaemic disease of the snakes which was resulting in high mortality and con- siderable financial loss (Cooper & Leakey, 1976). The veterinary profession has, until recently, been reticent to involve itself in lower vertebrate work but the situation is now changing and there are a number of veterinary surgeons, both practising and academic, who specialise in such fields as fish pathology or avian medicine. Zoonoses Work on these diseases is of great importance and is an example of a field where there is good liaison between the veterinary and medical professions and close links with others in allied disciplines. A few examples will suffice. A number of parasites can infect man from fish (Reichenbach-Klinke & Elkan, 1965); as a result, in many countries, there is statutory control covering the inspection of fish for human consumption and research on these and other zoonotic problems. Reptiles and amphibians also can serve as reservoirs of disease of man and other animals. An example is the arbovirus disease western equine encephalomyelitis which can affect man and horses in America. This is probably prim- arily an avian infection, but it has been shown that in the absence of arthropod vectors, the virus can overwinter in the garter snake (Thamnophis sp.); in

Diseases of lower vertebrates and biomedical research

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