The Nile crocodile of the Okavango Delta in health and disease

Lovely, Colin James (2007-03)

Thesis (MSc)-- University of Stellenbosch, 2007.

Thesis

ENGLISH ABSTRACT: Crocodile farming has become an important industry in Southern Africa over the last three decades. The diseases occurring in farmed crocodiles have been well researched, which has contributed to the success of modern crocodile farming operations. However, very little research has been done on diseases in wild crocodiles, and the normal physiology and disease prevalence of wild crocodiles remains largely unknown. In this study Nile crocodiles were captured in the Okavango Delta, Botswana. Blood was collected and normal haematological and blood biochemical ranges were established for a subsample of the population (haematology n=38, biochemistry n=35). The ranges obtained were generally in line with those reported for other species and farmed Nile crocodiles, except for mean haematocrit and total protein, which were relatively low. Parameters were also compared between males and females, as well as between size classes. Females had significantly 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 had significantly higher blood glucose than juveniles. Cloacal swabs were collected (n=29), which were cultured to establish the normal intestinal flora of these crocodiles. The intestinal flora was found to be diverse, with a mean of 2.7 bacterial species per crocodile. No Salmonella were cultured. Approximately half the crocodiles (48.3 %) also had a fungal component to their intestinal flora. A probiotic was produced based on the normal intestinal flora of the wild crocodiles. The potential for this probiotic to reduce mortalities and improve growth in farmed hatchlings was tested in a controlled 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 examination for blood parasites (n=38). No clinically apparent sick crocodiles were observed. No antibodies to Mycoplasma crocodyli were detected. The prevalence of hepatozoonosis was 55.3 %. There was no significant difference in the h.aematological parameters of Hepatozooninfected and un-infected crocodiles.

AFRIKAANSE OPSOMMING: Oor die afgelope drie dekades het krokodil boerdery in Suiderlike Afrika gegroei tot 'n groat industrie. Baie navorsing is al op die siektes van krokodille onder boerdery omstandighede gedoen, wat tot die sukses van moderne krokodil boerdery bygedra het. Baie min navorsing is al oor die siektes van wilde krokodille gedoen, en die siektes en nonnale fisiologie van wilde Nyl krokodille bly hoofsaaklik onbekend. In hierdie studie was Nyl krokodille in die Okavango Delta, Botswana, gevang. Bloed was getrek en die normale waardes vir 'n sub-seksie van die bevolking se hematolgie (n=38) en bloed biochemie (n=35) was vasgestel. Die waardes was vergelykbaar met die van Nyl krokodille onder boerdery omstandighede, sowel as waardes wat al van ander spesies geraporteer is, behalwe vir gemiddelde hematokrit en totale proteme, wat laag was. Parameters was tussen mannetjies en wyfies sowel as tussen verskillende groottes vergelyk. Wyfies het merkwaardig hoer gemiddelde rooiseltelling, eosinofiele, totale protein, en kalium as ma1metjies gehad. Sub-volwassenes het merkwaardig hoer gemiddelde hematokrit, hemoglobin, eosinofiele, basofiele, totale protern, globulien, natrium en kalium as jaar-oud en jong krokodille gehad. Jaar-oud krokodille het merkwaardige hoer bloed glukose as jong krokodille gehad. Kloak deppers was versamel (n=29), en kwekings gedoen om die normale dermkanaal flora vas te stel. Daar was 'n bree spektrum van dermkanaal flora, met 'n gemiddeld van 2. 7 bakterie spesies per krokodil. Geen Salmonella was gei"soleer nie. Daar was een of meer ftmgi van 48 .3 %van die deppers geYsloeer. 'n Probiotikum was gemaak, gebaseer op die normale dermkanaal flora van die wilde krokodille. Die vermoe van die probiotikum om sterftes te verminder, en groei te verbeter, was op klein krokodile onder intensiewe omstandighede getoets. Daar was geen voordeel daarin gevind. 'n Siekte opname was op wilde krokodille gedoen deur (i) 'n algemene kliniese ondersoek (n=l44), (ii) serologiese toetse vir mikoplasmose (n=30), en (iii) bloedsmeer ondersoek vir bloedparasite (n=38). Geen ooglopend siek krokodille was tydens bemonstering gevind, en daar is geen teenliggame teen Mycoplasma crocodyli gevind. Die voorkoms van Hepatozoon pettiti was 55.3 %. Daar was geen betekenisvolle verskil tussen die hematologie van die Hepatozoon-besmette en nie-besmette krokodille nie.

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