SURVEY FOR TRYPANOSOMES IN BLACK RHINOCEROS

Transcription

1 Journl of Wildlife Diseses Vol. 17, No. 4, October, SURVEY FOR TRYPANOSOMES BLAK RHOEROS (Diceros bicornis) B. LAUSEN, Veterinry Reserch Lbortory, Kbete, Keny. Abstrct: Blood smples were tken from 39 blck rhinoceros (Diceros bicornis), usully soon fter they were cptured. The blood ws exmined microscopiclly for trypnosomes, nd most smples were tested for trypnosome serum ntibodies nd inoculted into smll lbortory nimls. Serum ntibodies were found in most nimls nd trypnosomes identified s Trypnosom brucei were found in 7 of 39 (18%) of the rhinoceros. Berenil (diminzene ceturte) did not effect complete elimintion of trypnosomes. In spite of tretment, one rhinoceros died of trypnosomisis. TRODUTION Trypnosomisis hs been reported in blck rhinoceros (Dice ros bicornis)3 6 nd wild niml trppers know tht these nimls, when exposed to stresses of cpture nd cptivity, succumb to cute trypnosomisis dys or even weeks fter they hve been removed from tsetse res. Hrthoorn recommended routine injection of Berenil u t cpture to eliminte trypnosomes from blck rhinoceros. The purpose of the present survey ws to obtin more informtion on the prevlence of nturl trypnosomisis in blck rhinoceros, to compre dignostic methods, nd to determine the sensitivity of the rhinoceros trypnosomes to Berenil, s trppers complin tht rhinoceros often chieve trypnosomisis in cptivity, even if they re injected with Berenil when cptured, before trnsfer to holding grounds in tsetse-free res. MATERIALS AND METHODS Blood smples were collected from 39 rhinoceros, 12 cptured in Tnzni, between October, 1968 nd Februry, 1969, 24 cptured in Keny between April, 1969 nd November, 1970 nd three held in cptivity in Nirobi. Informtion on ge, sex nd loction of cpture re given in Tble 1. The identifiction numbers re the sme s used in bcteriologicl survey of blck rhinoceros.2 Blood ws collected from n er vein, nd heprinized blood ws injected into rts, using 2 mlintrperitonelly (ip) nd 2 ml subcutneously (sc), nd into mice, 1 ml ip nd 1 ml sc. The numbers of rts nd mice re given in Tble 1. The blood ws lso used to prepre thick nd thin blood smers. All rhinoceros were injected intrmusculrly with pproximtely 7 mg Berenil per kg body weight before they were relesed into their pens. Reserch undertken within project of the Government of Keny nd the United Ntions Development Progrm, with the Food nd Agriculture Orgniztion s executing gency. (I) Present ddress: Stte Veterinry Serum Lbortory, BUlowsvej 27, DK 1870 openhgen V., Denmrk. cette. Hoechst AG, Frnkfurt (Min), Germny.

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3 Journl of Wildlife Diseses Vol. 17, No. 4, October, Thin blood smers, fixed in bsolute ethnol nd the thick smers, unfixed, were stined in 10% Giems solution for 45 mm, nd ech smer ws exmined - microscopiclly for trypnosomes for t lest 10mm. Serum ws exmined for T. brucci ntibodies. Serologicl methods included the cpillry gglutintion test (Ar nd the ltex gglutintion test (LAT). Inoculted rts nd mice were exmined for trypnosomes every second dy - by microscopy of wet blood smers. If no trypnosomes were found within the first 45 dys fter inocultion the niml ws regrded s negtive. In n ttempt to distinguish 7. brucei from 7. rhodesiense, blood incubtion ) infectivity test ws employed.t. Three of the T. brucei strins isolted )<+ -. S were subinoculted into rts nd cttle, one cow nd nine rts per isolte. When trypnosomes were demonstrted in blood of the cows nd rts, pproximte- 0) ly 5 dys lter, six of nine rts in ech, group were treted with Berenil, three t dose of 3.5 mg/kg nd three t 7 mg/ kg. Three rts from ech isolte were kept s infected controls. Two of the three cows were treted with 7 mg/kg Berenil when they becme prsitemic, pproximtely 5 dys fter T. brucei inocultion, the third ws kept untreted for clinicl observtions for 23 dys, then treted S O. with 7 mg/kg Berenil. RESULTS Trypnosomes were found in blood smers from 7 of :39 (18%) rhinoceros in the survey (Tble 1). Morphologiclly, ll isoltes were identified s members of I the 7. brucei group. Thirty-two of the 33,... #{176} serum smples tested o-c-c>..... for serum n- < O - O 0? O tibodies were positive. F ive of 26 biood. smples injected into mice nd rts yield- ed isoltes of T. brucei. All the rhinoceros - S in which trypnosomes were found were II II II II ii subdults. The rts tht were injected with blood. - Lt O O tken. directly from the rhinoceros

4 584 Journl of Wildlife Diseses Vol. 17, No. 4, October developed prsitemi between 15 nd 32 dys fter inocultion. The trypnosomes did not kill the rts nd the prsites could be reisolted from their blood for severl months fter inocultion. Signs of trypnosomisis in rhinoceros. Only one of the nimls in the survey from which trypnosomes were isolted ctully died of trypnosomisis. Rhinoceros No. 10, weight pproximtely 350 kg, ws given :3.13 g Berenil i.m. when cught nd 8 dys lter further 2.1 g Berenil i.m. Aprt from minor bscess, the niml ppered norml until 25 dys fter it ws cptured, when it ws found with subcutneous edem over the foreprt of the body, especilly round the eyes nd lips. The niml ws in good flesh, the conjunctive were white, the respirtion ws 16/mm nd forced, nd the body temperture ws :39. The niml did not resist hndling during injection with 600 mg Smorin i.m. The swellings disppered within few dys. The number of trypnosomes decresed nd disppered from the blood smers within 4 dys fter tretment, but the niml remined depressed nd died 6 dys fter it first ws observed sick. The most remrkble finding t post mortem exmintion ws 10 X 10 X 10 cm shrply demrcted re of dry necrosis in the muscle where the Smorin hd been injected. Additionl blood smples were tken lso from two of the other infected rhinoceros while they were in their holding pens. No. 11, weight bout 250 kg, ws given 2.1 g Berenil (8.4 mg/kg) just fter cpture nd four dys lter the dose ws repeted. Blood smers tken on dy 12 nd dy 14 fter cptivity contined few trypnosomes, but trypnosomes were not demonstrted in blood smers tken on the dy 21, just before the niml died of septicemi.2 In No. 18, no trypnosomes were seen in blood smers on dy 21 nd dy 22 fter cptivity. The niml died on dy 23 but showed no specific necropsy findings, nd no trypnosomes were seen in tissue smers. The brin ws not exmined for trypnosomes. Berenil sensitivity tests. ttle subinoculted for the Berenil sensitivity test developed prsitemi within 2-3 dys. Only the cow injected with strin 13 ws exmined cliniclly. On the third dy it hd n elevted body temperture of 40. No other signs of disese were observed. Trypnosomes could be seen in wet blood smers from 3 to 6 dys fter inocultion. From 7 to 23 dys, when it ws treted with 1 mg/kg Berenil, trypnosomes could be demonstrted only by subinocultion into mice. It ws not possible to demonstrte ny trypnosomes in the rts inoculted with blood from the cttle fter the cttle hd been treted with 7 mg/kg Berenil. All the rts treted with 3.5 mg/kg Berenil relpsed with prsitemi within dys, nd those treted with 7 mg/kg between 26 nd 34 dys, except the rts tht were inoculted with strin 20 which remined negtive for 45 dys fter they were given 7 mg/kg Berenil. Blood incubtion infectivity test. The results of this test indicted tht the trypnosome strin isolted ws T. brucei rther thn T. rhodesiense. DISUSSION There re few published reports bout trypnosome infection in rhinoceros. Hore does not list the rhinoceros s host for trypnosomes, nd Weitz nd Glsgow9 plce the rhinoceros in group of fvored hosts for the tsetse fly but lso in group with low or no prevlence of trypnosome infections. The present dt would suggest tht T. brucei infections re not uncommon in blck rhinoceros. Isomet-midium chiorid. My & Bker, ligenhm, U.K.

5 Journl of Wildlife Diseses Vol. 17, No. 4, October, The popultions of rhinoceros in the survey res probbly ct s reservoirs for trypnosomes, but it is not known wht effect trypnosomes hve on freeliving rhinoceros. All the rhinoceros in the survey from which trypnosomes were isolted were pprently helthy when cught nd, possibly, trypnosomes only become pthogenic when rhinoceros re stressed by other fctors, e.g., drought, cpture, etc. Six of seven rhinoceros in which trypnosomes were demonstrted died of vriety of resons, while in the entire survey only two others died. Only the deth of No. 10, however, could be relted directly to trypnosomisis. All the deths occurred within 3 months fter cpture. While trypnosomes were found in ll blood smers from rhinoceros blood smples which produced trypnosomisis in lbortory nimls, there does not seem to be ny correltion between the biologicl nd serologicl tests. If the serum ntibody titers re compred with titers from cttle experimentlly exposed to T. brucei, it is found tht the titers re rther high in most of the rhinoceros. Animls Nos. 24 nd 25 kept in tsetsefree res hd low titers compred with most of the free-rnging nimls, evidence tht the titers my decline when rhinoceros re not regulrly exposed to trypnosomes. The only serum smples without trypnosome ntibodies ws from No. 28 which ws cptured when only few months old. Although the tested strins do not show ny prticulr resistence to Berenil, the repeted blood smpling from rhinoceros Nos. 10 nd 11 indicte tht it ws not possible to eliminte the trypnosomes completely from the rhinoceros nd, the observtion tht rhinoceros re extremely difficult to get bck on their feet fter they hve been sick, mkes it importnt to keep the nimls under very close observtion during the first four weeks of cptivity. The losses from trypnosomisis mong rhinoceros re possibly due more to lte tretment thn to wrong tretment. On the other hnd, depression nd deth of rhinoceros fter drugs pprently hve clered the trypnosomes from the blood strem, my relte to invsion by 7. brucei of the centrl nervous system. It my be worthwhile to consider tretment of such cses with drugs ble to pss the blood-brin brrier. The observed prevlence of T. brucei in rhinoceros, nd the filure to demonstrte T. congolense nd T. vivx in nimls from res like Kiboko where T. congolense nd T. vivx re the predominnt trypnosome species,5 my be evidence for prticulr susceptibility of the rhinoceros to infection with T. brucei. Acknowledgement The uthor would like to thnk the Director of Veterinry Services for permission to publish this survey, to Mssrs. Binz nd Rickmn from the WHO/Trypnosomisis Project, K41, Keny, for hving crried out the serologicl nd the blood incubtion infectivity tests, to Dr. G. Wrui from the Veterinry Reserch Lbortory, Kbete, who kindly provided lbortory fcilities nd help with trypnosome identifiction; lso to the personnel of the niml trpping compny, rr-hrtley & Sons, who were very coopertive nd helpful during the whole survey nd Dr. L. Krstd, who reviewed the mnuscript. LITERATURE ITED 1. BZ, G An evlution of the cpillry nd ltex gglutintion tests nd heterophile ntibody test for the detection of T. rhodesiense infections. Bull. World Helth Org. 47: 773.

6 586 Journl of Wildlife Diseses Vol. 17, No. 4, October, LAUSEN, B. nd WA. ASHFORD Bcteriologicl survey of blck rhinoceros (Diceros bicornis). J. Wildl. Dis. 16, 4, HARTHOORN, AM The chemicl cpture of nimls. Billiere Tindll, London, p HOARE, A The Trypnosornes of Mmmls. Blckwell, Edinburg. p KARSTAD, L., J.G. GROOTENHUIS nd E.Z. MUSHI Reserch on wildlife diseses in Keny Keny Vet. 2: McULLOH, B. nd P.L. ARHARD Mortlities ssocited with cpture, trnsloction, trde nd exhibition of blck rhinoceroses. Int. Zoo. Ybk. 9: RIKMAN, L.R. nd J. ROBSON The blood incubtion infectivity test: simple test which my serve to distinguish Trypnosom brucei from 7. rhodesiense. Bull. World Helth Org. 42: ROSS, J.P.J The detection of circulting trypnosoml ntibodies by cpillry tube gglutintion test. Ann. Trop. Med. Prsit. 65: WEITZ, B. nd J.P. GLASGOW The nturl hosts of some species of Glossin in Est Afric. Trns. Roy. Soc. Trop. Med. Hyg. 50: Received for publiction 19 October 1979