The Nile crocodile of the Okavango Delta in health and disease

[摘要] ENGLISH ABSTRACT: Crocodile farming has become an important industry in Southern Africa over the last threedecades. The diseases occurring in farmed crocodiles have been well researched, which hascontributed to the success of modern crocodile farming operations. However, very littleresearch has been done on diseases in wild crocodiles, and the normal physiology and diseaseprevalence of wild crocodiles remains largely unknown.In this study Nile crocodiles were captured in the Okavango Delta, Botswana. Blood wascollected and normal haematological and blood biochemical ranges were established for a subsampleof the population (haematology n=38, biochemistry n=35). The ranges obtained weregenerally in line with those reported for other species and farmed Nile crocodiles, except formean haematocrit and total protein, which were relatively low. Parameters were alsocompared between males and females, as well as between size classes. Females hadsignificantly greater mean red cell cotmt, eosinophils, total protein and potassium than males.Subadults had significantly greater mean haematocrit, haemoglobin, eosinophils, basoph.ils,total protein, globulin, sodium and potassium than yearlings and juveniles. Yearlings hadsignificantly higher blood glucose than juveniles.Cloacal swabs were collected (n=29), which were cultured to establish the normal intestinalflora of these crocodiles. The intestinal flora was found to be diverse, with a mean of 2.7bacterial species per crocodile. No Salmonella were cultured. Approximately half thecrocodiles (48.3 %) also had a fungal component to their intestinal flora. A probiotic wasproduced based on the normal intestinal flora of the wild crocodiles. The potential for thisprobiotic to reduce mortalities and improve growth in farmed hatchlings was tested in acontrolled experiment. No significant beneficial effect was obtained.A disease survey was carried out on the wild crocodiles by (i) a general clinical examination(n=144), (ii) serological testing for mycoplasmosis (n=30), and (iii) bloodsmear examinationfor blood parasites (n=38). No clinically apparent sick crocodiles were observed. Noantibodies to Mycoplasma crocodyli were detected. The prevalence of hepatozoonosis was55.3 %. There was no significant difference in the h.aematological parameters of Hepatozooninfectedand un-infected crocodiles.

[发布机构] Stellenbosch University