Field evaluation of parvaquone against naturally occurring East Coast fever

Parvaquone (Clexon Cooper) was clinically tested for efficacy as a treatment for East Coast Fever (Theileria parva parva infection) in naturally infected cattle. The drug showed a suppressive effect on Theileria schizonts and piroplasms. A recovery rate of 79% was recorded. Best results were obtained when Clexon treatment was initiated in the early stage of the disease, before many red blood cells were invaded and before respiratory distress was evident. A carrier state in animals recovered from East Coast Fever is suspected.     

Treatment of East Coast fever: a comparison of parvaquone and buparvaquone

Two trials were conducted to compare the efficacy of parvaquone and buparvaquone for the treatment of naturally acquired East Coast fever (ECF, Theileria parva infection) which, if untreated, is almost invariably fatal in European breeds of cattle. In the first trial 28 naive cattle were exposed in a paddock infested with ticks carrying a virulent form of the disease. Twelve were treated with each drug when they developed clinical ECF. All 24 cattle were cured. In the second study, 100 cases of ECF occurring naturally on farms in Kenya were treated, 50 with each drug. Parvaquone cured 44 (88%) buparvaquone cured 45 (90%). Intercurrent infections, predominantly anaplasmosis and bacterial pneumonia or scour, were treated specifically. It is concluded that parvaquone and buparvaquone are similarly effective in curing ECF and cure rates are maximised by accurate diagnosis and prompt treatment of both ECF and intercurrent infections.     

Chemotherapy of East Coast fever: parvaquone treatment of Theileria parva parva at intervals after infection

Groups of seven cattle were infected with Theileria parva stabilate and treated with parvaquone (20 mg kg-1 bodyweight) zero, four, eight, 12, 14 or 16 days after infection. Very early treatments resulted in a rapid recovery or no detectable parasitosis and some cattle were subsequently susceptible to homologous challenge. Treatments applied before extensive lymphoid or other organ damage had developed were successful and some cattle treated in advanced disease also recovered. Clinical pathological indications of liver or kidney damage were recorded very late in the disease suggesting that prompt diagnosis and treatment are more important than supportive therapy for survival. Treatment on day 8 after infection allowed the appearance of macroschizonts and a transient pancytopenia but no other disease signs. This group was solidly immune to challenge and this timing and treatment could be recommended for use in an infection and treatment method of immunisation.     

Comparison of long acting oxytetracycline and parvaquone in immunisation against East Coast fever by infection and treatment

Two groups of five cattle were immunised with a field isolate of Theileria parva as stabilate and simultaneously treated with long acting oxytetracycline or parvaquone in early clinical disease. The oxytetracycline group suffered a marked fall in leucocyte count and one animal died during immunisation. The parvaquone group suffered a less severe fall in leucocyte count and all survived. The surviving immunised cattle were immune to homologous challenge but susceptible to subsequent challenge with T p lawrencei.     

Chemotherapy of East Coast fever: parvaquone treatment of clinical disease induced by isolates of Theileria parva

Two experiments were carried out in which parvaquone was used to treat experimentally-induced acute clinical East Coast fever infections. In the first experiment, infections with Theileria parva parva (Kiambu 5) were induced by applying infected Rhipicephalus appendiculatus ticks or by inoculation of triturated infected-tick stabilate. The character of the disease was similar with both methods of infection and following a single treatment with parvaquone at 20 mg kg-1, 5 of 7 cattle in each group recovered. All untreated control cattle died. In the second experiment, 5 stabilate isolates from different locations within East Africa, and representative of the challenge likely to be met in the field, were used. Treatment was administered in 2 X 10 mg kg-1 doses 48 h apart. The isolates used were T. p. parva (Mbita), T. p. parva (Pugu), T. p. parva (Entebbe), T. p. lawrencei (Mara) and T. p. lawrencei/(Manyara); following treatment 3/7, 6/6, 6/7, 5/7 and 6/7 animals recovered, respectively. All untreated control cattle died. There was evidence of a difference in susceptibility of isolates to treatment, and some animals showed prolonged disease episodes. The nature of the response to treatment and the problems in treating a lympho-destructive disease are discussed.     

A clinical trial of buparvaquone in the treatment of East Coast fever.

A clinical trial was conducted to test buparvaquone (Butalex; Coopers Pitman-Moore) in the treatment of East Coast fever under field conditions in Kenya. Data from 229 cases were analysed following treatment with one (69), two (142) or three (18) doses at 2.5 mg/kg. The majority of cattle (95.2 per cent) were exotic (Bos taurus) or improved (Bos taurus cross Bos indicus) and 39.3 per cent were infected with Anaplasma marginale. There was an overall recovery rate of 85.6 per cent, with 90.1 per cent recovering following one treatment and 75.4 per cent recovering following two treatments. At a follow-up visit three to six months after completion of the trial data was obtained on 224 cases. Thirty had died, 13 of which were reported to have been from East Coast fever, nine had been sold and six slaughtered. Of the remaining 146, 86.3 per cent were in good condition, 13.7 per cent fair and 2.0 per cent in poor condition. A two dose regimen was most effective and should be recommended except in very early cases or those under direct veterinary supervision.     

Comparative studies of the efficacy of parvaquone and parvaquone-plus-frusemide in the treatment of Theileria parva infection (East Coast fever) in cattle

Comparative studies of the efficacy of parvaquone (Parvexon) and parvaquone-plus-frusemide (Fruvexon) Bimeda Chemicals, Ireland, were done on 60 naturally infected cases of East Coast fever (ECF; Theileria parva infection in cattle). Small-scale dairy farmers in the peri-urban of Dar Es Salaam city reported ECF-suspected cases from March to mid-October 2001 and were treated with the two drugs alternately, as were diagnosed positive for ECF. Four sub-groups of 15 cattle each (early stage, 15; advanced stage, 15) were treated with parvaquone and parvaquone-plus-frusemide. Twenty-eight out of 30 (93.3%) cattle treated with parvaquone-plus-frusemide were cured, so do 24 out of 30 (80.0%) cattle treated with parvaquone without frusemide. Early diagnosis and prompt management of pulmonary signs, which accounted for 30.0% of total ECF cases is advised in order to improve cure rates. Unlike parvaquone without frusemide (Parvexon), parvaquone-plus-frusemide (Fruvexon) proved useful in the management of pulmonary signs, hence, a drug of choice in the treatment of ECF cases that are accompanied by or are likely to manifest pulmonary signs.     

Identification of a target population for immunisation against East Coast fever in coastal Kenya

Two experiments were carried out to identify the target population of cattle for immunisation against East Coast fever (ECF) using the infection-and-treatment method. Firstly, a sentinel-calf study was used to determine the age window for ECF immunisation by determining ages at clinical detection of infection with Theileria parva. Six groups of five naive cross-bred (Bos taurus/Bos indicus) male calves, introduced at intervals of 2 months at a mean age of 26 days, were exposed to natural tick challenge on a high ECF-risk, small-holder farm in the coastal lowland, coconut-cassava agro-ecological zone of coastal Kenya. Secondly, a challenge study evaluated the relationship between the presence of T. parva antibodies and immunity. Ten indigenous adult Zebu cattle and nine Zebu young stock purchased from farmers in the same zone, and eight cross-bred calves (survivors of the sentinel-calf study) were challenged with 10 times the immunising dose of T. parva Marikebuni stock. Twenty-four of these 27 cattle had high antibody titres before challenge. Two cross-bred calves, obtained from an ECF-free area and seronegative to T. parva schizont antigen, also were challenged and used as susceptible controls. Twenty-five (83%) of the 30 sentinel calves contracted ECF over an age range of 36-116 days (mean 72 days). The remaining five calves died of other causes within 2 months of arrival on the farm. Fourteen of the 25 calves survived the infection and developed antibodies to T. parva. Despite tick control, seven of these 14 calves had a second episode of ECF and two died. In total, 13 of the 25 calves that contracted ECF died. Only one of 19 indigenous Zebu animals developed clinical ECF when challenged with T. parva Marikebuni (mild clinical signs with spontaneous recovery). Of the eight cross-bred survivors from the first experiment, only one succumbed to ECF when challenged and it died. Both susceptible cross-bred calves developed severe clinical signs of ECF and one died. The experimental studies show that in the high ECF-risk areas of the coconut-cassava zone of coastal Kenya, immunisation against ECF in cross-bred (B. taurus/B. indicus) cattle should be targeted at an early age (preferably within 1-2 months of birth).     

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 to 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.     

Skin nodules in East Coast fever.

A skin eruption developed in five calves with advanced experimental East Coast fever (ECF) (Theileria parva infection). In three cases the eruption was due to intradermal nodules containing numerous theilerial schizonts, in one animal the nodules contained abscesses filled with Demodex mites, and in the fifth calf both types of nodules were present. No nodules were seen in 15 other experimental cases of ECF, which generally died or were killed in an earlier stage of the disease. It is postulated that demodicosis may become apparent in healthy carriers of the mite in the course of ECF, because of immuno-depression caused by the latter disease.     

Long-acting oxytetracycline prophylaxis to protect susceptible cattle introduced into an area of Kenya with endemic East Coast fever

Two field trials were carried out in successive years at the Ngong Veterinary Farm, Kenya, in which young cattle, previously unexposed to tick-borne diseases, were introduced into an area with endemic East Coast fever while protected by a series of injections of a long-acting oxytetracycline. In 1984, 12 animals which received injections of 20 mg/kg of the drug on days 0, 7, 14 and 21 after introduction, together with 12 untreated controls, were exposed without tick control until clinical disease occurred. All 12 control animals contracted East Coast fever by day 24 and 10 of them died. Five of the 12 injected animals had detectable parasites, and one of them required antitheilerial treatment. In 1985, four groups of 10 calves were introduced. One group received injections of 20 mg/kg of oxytetracycline on days 7 and 14, one group received injections on days 7, 14 and 21, and a third group received injections on days 7, 12 and 17; the fourth group (controls) had no treatment until clinical disease occurred. By day 35 all the control animals had contracted the disease and one had died despite antitheilerial treatment. Three injections of oxytetracycline suppressed the disease so that mild reactions occurred in only four animals in each group, but two injections failed to prevent severe reactions in two animals and mild reactions in four others.(ABSTRACT TRUNCATED AT 250 WORDS)     

Retrospective observations on the transmission of East Coast fever in Zimbabwe

Summary Records of 283 outbreaks of East Coast fever in Zimbabwe in the period 1914 to 1946 reveal that transmission of infection occurred throughout the year with peaks in January to March and May to July. The high level of transmission in January to March coincides with the known seasonal occurrence of adultRhipicephalus appendiculatus. It is suggested that transmission at other times of the year may have been effected by a population ofR. appendiculatus which did not exhibit a strictly seasonal life-cycle and has since been eradicated.

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Observaciones retrospectivas sobre la transmision de fiebre de la costa este en zimbabwe

Resumen Los registros de 283 brotes de Fiebre de la Costa Este en Zimbabwe en el periodo 1914–1946 revelaron, que la transmisión de la enfermedad ocurrió durante todo el a?o, con aumentos en enero-marzo y mayo–julio. El nivel alto de transmisión enenero-marzo coincide con la conocida ocurrencia estacional deRhipicephalus appendiculatus adultos. Se sugiere que la transmisión en otras épocas del a?o, podrían haber sido afectadas por poblaciones deR. appendiculatus el cual no exhibe cidos de vida estrictos y que ha sido erradicado.

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Observation a posteriori sur la transmission au zimbabwe de la theileriose

Résumé Les relevés de 283 foyers de la theileriose au Zimbawe durant la période 1914–1946 ont révélé que la transmission de l'infection s'effectue tout au long de l'année avec des pointes en janvier–mars et mai–juillet. Le haut degré de transmission de l'infection en janvier–mars co?ncide avec la fréquence saisonnière connue desRhipicephalus appendiculatus adultes. Ce fait suggère que la transmission pendant les autres époques de l'année pouvait avoir été réalisée par une population deR. appendiculatus qui ne possédait pas un cycle strictement saisonnier et qui a été éliminée depuis lors.

     

East Coast fever immunisation field trial in crossbred dairy cattle in Hanang and Handeni districts in northern Tanzania

East Coast fever (ECF) causes considerable mortality and production losses in the Tanzania smallholder dairy sector and limits the introduction of improved dairy breeds in areas where the disease is present. The infection and treatment method (ITM) was adopted by smallholder dairy farms for ECF immunisation in Hanang and Handeni districts of Tanzania. This study recorded incidence rates for ECF and other tick-borne diseases (TBDs) for ECF-immunised and non-immunised cattle between 1997 and 2000. Approximately 80% of smallholder households from both sites (n?=?167) participated in this longitudinal study, with immunisations carried out at the request of the livestock owners. Efficacy of ITM for preventing ECF cases in these crossbred dairy cattle was estimated at 97.6%, while that for preventing ECF deaths was 97.9%. One percent of the cattle developed clinical ECF as a result of immunisation. Since ECF immunisation permits a reduction in acaricide use, an increase in other TBDs is a potential concern. Sixty-three percent of farmers continued to use the same acaricide after immunisation, with 80% of these reducing the frequency of applications. Overall, 78% of farmers increased the acaricide application interval after immunisation beyond that recommended by the manufacturer, resulting in annual savings in the region of USD 4.77 per animal. No statistical difference was observed between the immunised and non-immunised animals in the incidence of non-ECF TBDs. However, immunised animals that succumbed to these diseases showed fewer case fatalities. ITM would therefore appear to be a suitable method for ECF control in Tanzania's smallholder dairy sector.     

Clinical and diagnostic features of East Coast fever (Theileria parva) infection of cattle

East Coast fever is a tick-borne protozoal disease affecting cattle in a large part of East and Central Africa. Since the vector occurs over an even wider range there is considerable potential for the disease to spread to countries which are currently disease free. This article, describing the clinical and diagnostic features of East Coast fever, may remind authorities in these countries of the potential hazards posed by the disease.