Comparison of indirect fluorescent antibody test and enzyme linked immunosorbent assay in the detection of exposure of cattle to Theileria parva in Kenya.

Appraisal of the indirect fluorescent antibody test (IFAT) and antigen enzyme linked immunosorbent assay (ELISA) serological tests as carried out to detect cattle exposed to Theileria parva at the National Veterinary Research Centre, Muguga (NVRC), Kenya is reported. Using sera from T. parva naive cattle and cattle experimentally exposed to T. parva, the two tests were appraised in terms of their sensitivity and specificity. IFAT and ELISA had the same sensitivity of 90% while ELISA had a higher specificity (90%) than IFAT (80%). A comparison was also made of the capability of the two tests to detect exposure of dairy cattle to T. parva prior to immunization against East Coast fever (ECF). The positive outcome from the IFAT was significantly higher (chi 2 = 30.36; P < 0.001) than that from the ELISA. The agreement between the two tests was low (Kappa = 0.21). The two tests indicated a higher risk of ECF in the study area than was expected. Indications are that the ELISA has been effectively adopted at NVRC.

Cost analysis of immunisation against east coast fever on smallholder dairy farms in Kenya.

A spreadsheet model was developed and used to estimate the total cost of immunising cattle against East Coast fever (ECF) based on the infection-and-treatment method. Using data from an immunisation trial carried out on 102 calves and yearlings on 64 farms in the Githunguri division, Kiambu district, Kenya, a reference base scenario of a mean herd of five animals, a 10% rate of reaction to immunisation and a 2-day interval monitoring regimen (a total of 10 farm visits) was simulated. Under these conditions, the mean cost of immunisation per animal was US$16.48 (Ksh 955.78); this was equivalent to US$82.39 (Ksh 4778.90) per five-animal farm. A commonly reported reactor rate of 3% would decrease the cost of US$14.63 (Ksh 848.29) per animal. Reducing the number of farm monitoring visits from 10 to 7 would reduce the total cost by 10%, justified if farmers are trained to undertake some of the monitoring work. The fixed costs were 53% of the total cost of immunisation per farm. The cost of immunisation decreased with increasing number of animals per farm, showing economies of scale.

Pharmaceutical quality of anthelmintics sold in Kenya.

Nine anthelmintic products in pharmacies and from agricultural merchants in Kenya were tested for pharmaceutical quality. The concentration of active drug was compared with the claim on the label, and the variability of several products was tested between batches and between bottles within the same batch. All the products purchased claimed to contain levamisole but its mean (sd) concentration varied from 0 to 118.0 (13.3) per cent of the claimed. The concentration of levamisole in different batches of the same product ranged from 0 to 85.4 per cent of that claimed. One product consisting in part of mebendazole was found to contain 73.2 (9.4) per cent of the claimed concentration of this active component and two products consisting in part of oxyclozanide were found to contain 106.0 (14.4) and 120.6 (6.1) per cent of the expected concentration of oxyclozanide.

Isolation of the causative agent of heartwater (Cowdria ruminantium) from three Amblyomma species in eight Districts of Kenya.

Thirteen isolates of Cowdria ruminantium were made from eight different Districts of Kenya by four different isolation methods. Feeding adult Amblyomma species ticks derived from nymphs collected in the field and the inoculation of homogenates prepared from adult field ticks had the highest success rate. The reattachment of adult ticks collected in the field was successful on only one of five attempts, and the subinoculation of blood from suspected heartwater carriers was unsuccessful. Seven of the isolates were derived from A variegatum ticks, four from A gemma, one from A lepidum and one from a mixed pool of the last two species. This is the first report of the isolation of C ruminantium from A gemma ticks, and the first report of its transtadial transmission from nymphal to adult A gemma.

A mild Theileria parva parasite with potential for immunisation against East Coast fever.

Twenty-three Friesian cattle were inoculated subcutaneously anterior to the left prescapular lymph node with 1 ml of a mild isolate of Theileria parva. The cattle developed low macroschizont parasitosis but no clinical reaction was observed. Thirty-five days later the cattle were grouped into five groups and challenged with five different Theileria parva isolates (four cattle-derived Theileria and one buffalo-derived Theileria). The cattle were all solidly immune to challenge with the cattle-derived Theileria isolates but three out of five of the cattle challenged with the buffalo-derived parasite died of theileriosis. All ten non-immunised control cattle developed severe theileriosis and were treated with buparvaquone (Butalex; Pitman-Moore).

Assessing the economic impact of immunisation against East Coast fever: a case study in coast province, Kenya.

The cost of immunising cattle against East Coast fever by the infection and treatment method has been calculated for a pilot scheme in Kaloleni Division of the Coast Province of Kenya by using a spreadsheet model. The cost was calculated to be KSh 544 (US$25) per animal (in 1990 values). If a farmer were to bear all this cost, immunisation would be financially profitable in grade cattle, but the benefits of immunisation would not be sufficient to justify the immunisation of zebu cattle. For these animals, the cost of immunisation would have to be in the range of KSh 230 to KSh 415 per animal, or the farm-gate price of milk would have to increase by at least 80 per cent from KSh 7.50 to 13.50/litre, or the government would have to subsidise the cost either partially or fully. The first two possibilities are realistic, because the costs of routine immunisation are likely to be lower than for the pilot scheme, and because the increasing demand for milk is likely to push up prices in the liberalised markets. If both the grade and zebu cattle in Kaloleni Division were targets for immunisation, it is estimated that there would be 14,500 head for immunisation annually, costing an estimated KSh 8 million. The spreadsheet model used to assess the economics of immunisation in the Kaloleni Division could be applied to determine the government or private veterinary service charges for immunisation that would be financially profitable to farmers in a defined cattle production system in any division, district or country. The model could also be used to estimate the annual total number of cattle for immunisation in a target cattle production system and thus help with the financial planning for the exercise.

Theileria parva carrier state in naturally infected and artificially immunised cattle.

Rhipicephalus appendiculatus adult ticks, collected in the field from zebu (Bos indicus) and exotic (Bos tarus) cattle with high antibody titres to Theileria parva schizont antigen, transmitted Theileria parva infection typical of East Coast fever to susceptible cattle. Uninfected R. appendiculatus nymphs applied to naturally recovered zebu and exotic cattle kept under tick-free conditions in the laboratory for 16 and 7 months respectively, transmitted fatal theileriosis to susceptible cattle. Cattle immunised by the infection and treatment method were shown to be carriers of Theileria parva by examination of the salivary glands of ticks applied to them and by tick transmission. Three and 7 months after immunisation, Theileria parva infected lymphocytes were established in vitro from peripheral blood lymphocytes. This was the first demonstration, in vitro, of the existence of schizonts in Theileria parva (East Coast fever) infection carrier status. These studies show that cattle from endemic and epidemic areas of East Coast fever (ECF) become carriers thereby maintaining the T. parva population. The relevance of the findings in this study to the control of ECF by dipping, immunisation and treatment is discussed.

Trial of the efficacy and immunological response to an inactivated mycoplasma F38 vaccine.

Goats on two zero grazed farms carrying 1621 animals with a history of contagious caprine pleuropneumonia were subjected to a vaccine trial with an inactivated mycoplasma F38 vaccine. The results indicated that the vaccine produced an immune response, that it was very effective in reducing morbidity and mortality rates, and that a booster dose one month after the first dose of vaccine gave extra protection.

Observations on rinderpest in Kenya, 1986-1989.

Rinderpest was confirmed in Kenya in 1986, 1987, 1988 and 1989. Three epidemiologically distinct events appear to have occurred: repeated outbreaks in West Pokot district related to cross-border movement of stock, an outbreak in Marsabit district in 1987 (thought to have been caused by illegal movement of cattle, possibly in vehicles, from countries further north) and a series of related outbreaks in and near Nairobi between 1988 and 1989 due to the unauthorized movement from abattoirs and holding grounds of slaughter stock possibly introduced from West Pokot or Marsabit. In West Pokot the disease affected unvaccinated calves and yearlings. In Marsabit cattle of all ages were affected. In August 1988, a major outbreak was confirmed in Kiambu and Kajiado districts in central Kenya, near Nairobi. At the same time a provisional diagnosis of rinderpest was made in a herd of cattle at a slaughterhouse in Nairobi. Rinderpest virus was isolated from sick cattle in all the outbreaks. Experimental infection of susceptible cattle with the Kiambu isolate demonstrated this to be of low virulence. Emergency vaccination and quarantine measures instituted immediately after confirmation eliminated clinical disease within three to four weeks in West Pokot, Kiambu and Nairobi. In Kajiado, however, the disease persisted for at least nine months, during which time a series of virus isolates was recovered. There was no evidence of infection in susceptible wildlife. This increase in the incidence of rinderpest in Kenya in recent years serves to highlight the problems of control and the need for concerted efforts to eradicate the threat of the disease from East Africa.

Further evaluation of the use of buparvaquone in the infection and treatment method of immunizing cattle against Theileria parva derived from African buffalo (Syncerus caffer).

Three experiments were undertaken to determine the efficacy of different doses of buparvaquone in the infection and treatment immunization of cattle against Theileria parva derived from African buffalo (Syncerus caffer). Two of these experiments also compared buparvaquone with standard doses of long- and short-acting formulations of oxytetracycline. In addition, different dilutions of stabilates were used in the experiments. In the first experiment, a 10(-1.0) dilution of stabilate was used to infect groups of cattle treated with buparvaquone at doses of between 5 and 0.625 mg kg-1 body weight (bwt) on Day 0 after infection. All control cattle developed severe theileriosis and none of the treatment regimes (including those utilizing long-acting oxytetracycline) prevented the development of theileriosis. Treatment with buparvaquone at 2.5 mg kg-1 bwt or oxytetracycline gave the most satisfactory results. In the second experiment when the sporozoite dose was reduced to 10(-2.0) dilution, buparvaquone treatment at 5 and 2.5 mg kg-1 bwt and short- and long-acting formulations of oxytetracycline reduced reactions greatly. While all the oxytetracycline treated animals produced a serological response and were immune to a 50-fold higher challenge with the immunizing stabilate, several animals in the buparvaquone groups did not show a serological response and were not immune to challenge. In the third experiment, groups of cattle were infected with 10(-1.2), 10(-1.4) and 10(-1.6) dilutions of stabilate and were treated with 2.5 mg kg-1 bwt of buparvaquone. No animals developed severe theileriosis and all seroconverted. On homologous challenge, however, two out of 14 cattle showed severe reactions. It was concluded that further work on immunization using buparvaquone treatment at 2.5 mg kg-1 bwt and 10(-1.6) dilution of the stabilate would have to be carried out before such a system could be used in the field.

Immunisation of cattle against theileriosis in Nakuru District of Kenya by infection and treatment and the introduction of unconventional tick control.

One hundred and one cross European-Boran cattle (50 cows and 51 calves), on a farm in Nakuru District, Kenya, were immunised against theileriosis using Theileria parva lawrencei and Theileria parva parva stocks from another district of Kenya. The stabilates used were T.p.lawrencei (Mara III) used at 10(-1.7) dilution and T.p.parva (Kilae) used at 10(-1.0) dilution. The stabilates were combined and inoculated simultaneously with a short-acting formulation of oxytetracycline hydrochloride given intramuscularly at 10 mg kg-1 body weight and was repeated on Day 4 after inoculation of the stabilate. Most of the theileriosis challenge on the farm was thought to be derived directly from the African buffalo (Syncerus caffer). Nine percent of the cattle had significant indirect fluorescent antibody (IFA) titres before the immunisation and 99% after immunisation. The immunised cattle were exposed to tick-borne disease challenge on the farm by withdrawal of acaricide cover. The immunised cattle were divided into five groups plus two susceptible control cows and two calves for each group. Cattle in four of the groups had acaricidal ear tags, each group having a different type, applied to both ears and the fifth group remained untagged. The animals remained without conventional acaricide application for 134 days. Ten out of 20 (50%) non-immunised control cattle became T.p.lawrencei reactors which only one out of 97 (1%) of the immunised cattle reacted. A frequent complication noted was mild infections due to unidentified Theileria sp. which required expert differentiation from T.parva infections. An additional group of ten steers whose tick load was removed by hand at weekly intervals was introduced 79 days after exposure; these had no tick control and four became T.p.lawrencei reactors. Of 12 calves born during the exposure period and without tick control, four became theilerial reactors and one died. The application of acaricidal tags however, reduced tick infestation levels considerably compared with untagged controls but did not prevent transmission of theileriosis with the possible exception of tags on Group 4. A number of transient low grade fevers were noted and attributed to Theileria sp., Ehrlichia bovis, Ehrlichia (Cytoecetes) ondiri and Borrelia theileri infections, none of which were fatal. One immunised animal died of acute dual infection of Babesia bigemina and Borrelia theileri after acaricide control by spraying was re-introduced but no Anaplasma infections were detected. An analysis of the economic effects of immunisation was made.

Detection of a carrier state in Theileria parva-infected cattle by the polymerase chain reaction.

Two sets of oligonucleotide primers, one derived from a repetitive sequence and the other from the gene encoding a 67 kDa sporozoite antigen of Theileria parva, were used to amplify parasite DNA from the blood of T. parva-infected carrier cattle using the polymerase chain reaction (PCR). PCR amplification products were obtained from 15 carrier cattle infected with one of 4 different T. parva stocks. Successful amplifications were performed using DNA from 2 cattle infected with T. p. parva Pemba Mnarani, 10 cattle infected with T. p. parva Marikebuni, 2 cattle infected with T. p. bovis Boleni and 1 animal infected with T. p. lawrencei 7014. No amplification products were obtained from any of 7 cattle which had been infected with the T. p. parva Muguga stock. A synthetic oligonucleotide, which hybridized specifically to T. p. parva Marikebuni DNA among 6 T. parva stocks tested, was designed using sequence data from within the region of the T. parva genome amplified by the repetitive sequence primers. The oligonucleotide was used to probe PCR products and to increase the sensitivity and specificity of carrier animal detection. Southern blot analysis using a T. parva repetitive sequence probe demonstrated the existence of restriction fragment length polymorphisms between parasites isolated from T. p. parva Marikebuni-infected carrier cattle. The use of the PCR and other methods of carrier animal detection are discussed.

Epidemiological observations on theileriosis following field immunisation using infection and treatment.

Thirty-seven high grade cattle were immunised against Corridor disease (Theileria parva lawrencei infection) on a farm with a history of heavy and often lethal theilerial challenge. Nineteen cattle were immunised by treating with two doses of long-acting oxytetracyclines given at 20 mg/kg on days 0 and 4 after sporozoite stabilate inoculation, while the other 18 were treated with naphthoquinone buparvaquone, given as a single dose of 2.5 mg/kg simultaneously with stabilate inoculation. All the cattle underwent subclinical theilerial reactions with all but two developing high antibody titres on the IFAT test against T. parva schizont antigen by day 35 after the immunisation. Both buparvaquone and long-acting oxytetracycline appeared equally effective in the immunisation. To date, 26 months later, only two cases of theileriosis parasitologically characteristic of T. p. parva have been reported in the immunised cattle. Following the two cases, investigations showed that when uninfected Rhipicephalus appendiculatus nymphal ticks were deliberately fed on healthy resident cattle on the farm, the resultant adult ticks transmitted acute and lethal theilerial infections to five out of five susceptible cattle. The resultant infections were parasitologically characteristic of T. p. parva infections. Furthermore, the monoclonal antibody profiles of schizont infected cell lines from these infections appeared to be characteristic of T. p. parva. It was thus concluded that resident cattle on the farm could be a potential source of T.p. parva infection which had broken through the immunity of T.p. lawrencei immunised cattle and could constitute a reservoir of theilerial infection for ticks and hence to susceptible stock on the farm.

Low-dose oral administration of human interferon alpha can control the development of Theileria parva infection in cattle.

Two natural human interferon alpha preparations, (nHuIFN-alpha [Cantell]) and (nHuIFN-alpha [ISI]), were used for the oral treatment of cattle experimentally infected with Theileria parva parva. In the first experiment, 8 Friesian bulls were inoculated with a 1 in 10 dilution of a sporozoite stabilate of T.p. parva (Marikebuni) stock. Four of the cattle were treated daily with 1 international unit/kg body weight (i.u./kg bwt) of nHuIFN-alpha (Cantell) from day -2 to day 8 p.i. None of the 4 calves given IFN developed clinical theileriosis, but 3 of the 4 control calves died of theileriosis while the fourth had a mild infection. Three of 4 treated calves and the 1 surviving control calf developed a detectable antibody response to T.p. parva schizont antigen but, on challenged with a 10-fold higher dose of stabilate, the surviving control animal and only 1 of the 4 treated calves proved to be immune. In a second experiment, 4 groups of 4 calves were inoculated with the same stabilate dilution. Three treatment groups were given either 1 i.u. nHuIFN-alpha (Cantell), 1 i.u. nHuIFN-alpha (ISI), or 10 i.u. nHuIFN-alpha (ISI)/kg bwt from day -2 to day 8 p.i. once daily and the fourth group were controls. Clinical theileriosis occurred in 2 controls, 2 calves given 10 i.u. nHuINF-alpha (ISI), 1 calf given 1 i.u. nHuIFN-alpha (ISI) and no calves given 1 i.u. nHuIFN-alpha (Cantell)/kg bwt. Of these, 2, 1, 0 and 0 cattle died in the respective groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Parasite survey of eight wild animals in the Ruma National Park.

Eight game animals representing seven species in the Ruma National Park in South Nyanza, Kenya, were examined for the presence of blood protozoa, ectoparasites, and helminthic and coccidian endoparasites using standard parasite-identification methods. Haematological parameters were also determined. The oribi was positive for Trypanosoma brucei ssp. and the reedbuck for T. congolense. No other blood protozoans were found. Strongyle eggs were found in the faeces of all species except the water buck. Five of eight animals harboured liver flukes and five were parasitized by ticks of the genus Amblyomma. One roan antelope was anaemic, but the other animals had haemoglobin levels within the normal range and appeared to be in a good state of health.

Integrated control of ticks and tick-borne diseases of cattle in Africa.

The problems caused by tick and tick-borne diseases for livestock particularly cattle on the African continent are described and discussed. The control of ticks and tick-borne diseases must receive high priority in Africa with regard to both research and control application because of their widespread distribution in areas of high livestock potential and productivity. The conventional methods of tick and tick-borne disease control are discussed and are found to be inadequate in the conditions prevailing in Africa. Methods of integrated control are suggested and discussed in light of recent development in control methods and those still under development. Any one of these methods may not be adequate to control the problem on its own but when several of the methods are combined an economic and robust integrated control is likely to result. Encouragement is given to attempt this approach in Africa to solve what must be the largest animal health problem of livestock remaining in the world.

A recent outbreak of rinderpest in East Africa.

Rinderpest was brought under control in Kenya in 1976 but in April 1986 an outbreak of the disease occurred in cattle in Western Kenya, five kilometres from the Kenya-Uganda border. This was the first confirmed field outbreak of the disease in Kenya after a lull of over 10 years. Clinical disease was confined to unvaccinated zebu calves aged six to eight months from which rinderpest virus was isolated. High titres of antibodies to rinderpest virus were demonstrated in sera collected from sheep and goats that were grazing together with the affected cattle herds; there was, however, no evidence of clinical disease in these small ruminants and wildlife species in the affected area. The disease outbreak was rapidly stamped out by quarantine and vaccination.

Corynebacterial infection of cattle in Kenya.

Skin infections in cattle caused by Corynebacterium ovis, either as the main pathogen or in association with other organisms, was investigated on a Kenya ranch. The morbidity rate was approximately 25% involving more than 3,000 cattle and the condition appeared to be highly infectious. Three treatment regimes were instituted and the most effective proved to be lancing and irrigating the large abscesses with iodine solution.