Br. vet.J. (1996). 152, 477

SHORT COMMUNICATION

ACUTE TRYPANOSOMOSIS IN A SEDENTARY HERD ON THE TSETSE-FREE JOS PLATEAU, NIGERIA

A. U. KALU

Department of Vete~nm)' Public Health and Preventive Medicine, University of Maiduguri, P.M.B. 1069, Maidugu~, Borno State, Nige)~a

KV.~WORDS: Trypanosolnosis; T)ypanosoma vivax; haematophagous; Diptera; Glossina.

Trypanosomosis is reported here for the first time among intensively-reared (sedentary) cattle on the tsetse-fl'eeJos plateau. The disease which affected 4-year- old Friesian dairy cows was acute and resulted in anaemia, abortion and death. T~ypanosoma vivax was identified as the aetiologic agent. Sensitivity tests in caprine hosts showed the parasite was resistant to diminazene aceturate (Berenil, Hoechst) but sensitive to isometamidium chloride (Samorin, May & Baker).

The Sahel vegetational zone and the plateaux ofJos, Mambila and Obudu are regarded as tsetse-flee areas (Iwuala & Ajezie, 1980) and evidence of trypano- somosis among sedentary livestock in these areas is lacking. This report presents observations ola some aspects of the disease in an intensively-managed dai W (Friesian) farm sited oll theJos plateau.

The West African Milk Company (WAMCO) PLC farm in Vom (9 ° 45 ' North, 8 ° 47 ' East; 1280 m above sea level) is divided into paddocks separated by barbed wire and fortified by electric fencing. The animals, which had been imported 2 years prior to the infection, were immunized against common diseases using vac- cines produced at the National Veterinary Research Institute (NVRI) laboratories at Vom and were inspected regularly by the Company's veterinary consultant. A report of ill-health in the cattle was received from WAMCO citing dullness, leth- arD, and emaciation which-had been observed approximately 8 Weeks earlier; three animals had died within 2 weeks and during the same period milk yields had been reduced by 11.4% from the optimal daily production level of 8.8 kg per animal. Within a week of the appearance of the clinical signs, a tentative diagnosis of babesiosis had been made and treatment instituted with diminazene.

Two urlits consisting of 115 animals were affected. Animals were examined clini- cally and blood and faecal samples collected. Blood was collected from every second animal by jugular venepuncture into bottles containing ethylene diamine tetra-acetic acid (EDTA) as anticoagulant. Diagnosis of infection was by parasito- logical techniques (thin and thick smears, buff T coat examination and the haema- tocrit centrifugation) described by Kalu et al. (1986). Blood from each sample was

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-178 BRITISII VE-I'ERINARY .]OURNAI., 152, -t

also inoculated into nvo adult albino rats, followed by microscopic examinat ion of smem's fronl tail b lood for up to 60 days. Giesma-stained thin fihns were examined to de t e rmine the species of tr}'panosonms. Packed cell w)lume (PCV) was esti- mated using a microlmenmtocr i t centr i fuge and reader . Examinat ion of faecal samples was by botla direct smear and concent ra t ion methods. Drug sensitivity tests on three t rypanosomes isolated fl'om three animals and from heavily parasit- ized samples were conduc ted in caprine hosts using diminazine and isomctamid- ium chloride. Diminazine at doses of 3.5 mg mad 7.0 mg kg-' body weight (b.w.) and i sometamidium chlor ide at 0.5 mg kg -~ b.w., were adminis tered intramuscul- arh' in infected test hosts. Ti-apping of tsetse and o the r biting flies was by use of three biconical traps and two prototypes of the NITSE trap (O m o o g u n , 19.~)0).

In addit ion to the clinical signs repor ted by the herd-owner, jugular pulsation, anaemia and abor t ion were observed in one cow. Out of 55 blood samples col- lected, nine (16.4%) were positive for ll}'pallosomes. T~3'pam,soma vivax was the only species encoun te red . Only. (me sample from a c()w with a parasi taemia of 4× 107 parasites per ml was infective to laboratory rats: both animals inocula ted with the specimen were positive on days 4 and 5 post infection, but the to :panosomes did not establish thereafter . Two tD, panosome-f ree cows were infected with Anrt- plasma mmgrinale and strongTle species. The PCV of tDl)anosome infected animals ranged between 20.0 and 35.0% with a mean of 27.3+4.7%. Th e mean value ior healt lw cows (range 27.0 to 40.0; mean 35.5+3.1%) was significantly h igher (P< 0.05). Resistance to diminazine was establislaed at the two dose levels (3.5 mg and 7.0 nag kg ~ b.w.) employed in all goats t reated with the drug. However, such animals becanae aparasitaemic within 4 days post therapy but the infection re- established 10-21 days later, d epend ing on dose. (_;oats t reated with isometamid- ium chlor ide became aparasitaemic within 8 days of t r ea tment and n o n e relapsed.

The herds were t reated with isometamidiunl chlor ide at 0.5 mg kg ~ b.w. and long-acting tetracycline (Terramycin LA, Pfizer) at 10 mg kg -~ b.w. on the basis of the above resuhs. The problem did not re-occur dur ing a 9 m o n th per iod of observation.

Tsetse flies have n o t been repor ted on any part of the Jos plateau and n o n e were caught dur ing several study visits over a 4-week period. Nevertheless, rear ing of Glossina palpalis palpalis and G. tachinoides has been underway for several },ears, at the Biological Contro l (BIGOT) project station of the Federal Minist D, of Agric- ulture and the In ternat ional Atomic E n e r ~ ' Agency (IAEA), Vienna. A few tsetse flies have been caught outside the station but n o n e was infected. Th e BIGOT station with colonies of laborat tnT-reared tsetse and the Nigerian Institute for Tl T- panosomiasis Research (NITR) laboratories (Vom) engaged in studies on all aspects of the pm-asite mad vectors of trypanosomosis, share a c o m m o n boundary mad each is within 1 km of the farln. Moreover , pastoral herds within the neigh- b o u r h o o d often break th rough the barbed wire fencing to reach the improved pasture of the farm leading to the installation of electric fences. Al though n o n e of these three potential sources of the ou tbreak was investigated, each has the capacity to precipitate it singly or in combinat ion . On the other hand, tal)anids and stomoxys flies and ticks are all prevalent in Vom mad trypanosomes, especially T. vivax, are known to be t ransmit ted th rough these mechanical inoculators (Wells, 1972).

TR~I'.kNOSOMOSIS ()N .[OS PL~\TEAU 479

In thc East African subregion, Roeder el al. (1984) have repor ted an outbreak of 7: v ivax in cattle grazing 400 km fi-om known Glossitm habitat in Ethiopia and con- cluded that transmission was due to o ther haema tophagous Diptera. Relapse infections lollowing diminazine therapy is COlllnlon trader field condit ions in Nigeria (Agn el al., 1989) and there have been similar reports of d rug resistance in Zambia (Chi tambo & Arakawa, 1992) mad o ther parts of East Africa (Schillinger, 1989). This repol't emphasizes the impor tance of careful screening of exotic il3"panosusceptible livestock impor ted into tsetse-free areas both on arrival and at regular intevvals.

A C K N O W L E D G E M E N T S

Facilities lot this study were provided by EEC Lome III grant, fin- the Control of Animal Tv}'panosomiasis in Nigeria.

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R~)I:.DH~., P. 1.., St:ol-r,.]. M. & PI.;Nc;RXM, R. (;. (1984). Acute 7"13'pamJsoma vivax infection of Ethiopian cattle in apparent absence of tsetse. Tropical Atdmal Health & Pmductimt 16, 141-7.

S~:t lu.I tx~a.R, D. (1989). The problem of tD'panocidal drug resistance. Kenya l'eterinaria~l 9, 21-4.

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(AcceptM Ira publicatimt 25 April 1995)