Parasites of domestic and wild animals in South Africa. XLV. Helminths of dairy calves on dry-land Kikuyu grass pastures in the Eastern Cape Province.

Successive pairs of approximately 4-month-old Friesland bull calves, raised under worm-free conditions, were exposed to helminth infection for 14 days on dry-land Kikuyu grass pastures at 28-day to monthly intervals, on a coastal farm in a non-seasonal rainfall region of the Eastern Cape Province. With the exception of one pair of calves exposed for 28 days, this procedure was repeated for 28 consecutive months from December 1982 to March 1985. The day after removal from the pastures one calf of each pair was slaughtered and processed for helminth recovery and the other 21 days later. Both members of the last four pairs of calves were killed 21 days after removal from the pastures. Sixteen nematode species were recovered from the calves, and infection with Ostertagia ostertagi was the most intense and prevalent, followed by Cooperia oncophora. The calves acquired the greatest number of nematodes from the pastures from June to October of the first year and from June to August of the second year of the survey. Few worms were recovered from the tracer calves examined from November or December to March or April in each year of the survey. The seasonal patterns of infection with Cooperia spp., Haemonchus placei, Nematodirus helvetianus, Oesophagostomum spp., O. ostertagi and Trichostrongylus axei were all similar and were negatively correlated to atmospheric temperature and evaporation. Slight to moderate arrest in the development of fourth stage larvae occurred from July to September in Cooperia spp., April to July in H. placei, and August to October in O. ostertagi and Trichostrongylus spp. during the first year of the survey. Too few worms were present in the second year to determine a seasonal pattern of arrest. Species survival during the hot and windy summer months appeared to be achieved via a combination of arrested larval development and an ageing residual population of adult worms in the host, and a small extant population of infective larvae on the pastures.

Incidence of Anoplocephala perfoliata in horses examined at an Irish abattoir.

The intestinal tracts of 363 horses were examined after slaughter at a horse abattoir. The presence or absence of Anoplocephala perfoliata and the sites of attachment were recorded. A total of 51 per cent of the horses had A perfoliata attached to the mucosa of the ileocaecal junction and/or to the caecal mucosa; 5 per cent of the horses had A perfoliata attached only to the mucosa of the ileocaecal junction, 24 per cent had A perfoliata attached only to the caecal mucosa and 22 per cent of the horses had A perfoliata attached at both sites. The degree of infestation did not appear to be influenced by the season or by the age, breed or source of origin of the horses. The lesions at the sites of attachment included congestion, oedema, ulceration, diphtheresis, mucosal thickening, eosinophil infiltration and fibroplasia. The severity of the lesions was exacerbated by increasing numbers of worms.

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)

Development of a prophylactic regime using long-acting tetracycline for the control of redwater and heartwater in susceptible cattle moved into an endemic area.

Thirty young crossbred steers were purchased from a tick-borne disease-free farm in South Africa, shown to be serologically negative to Babesia bigemina/bovis and Cowdria ruminantium, and moved to an experimental farm where babesiosis and heartwater were known to be endemic. The animals were allowed to graze as a herd on tick-infested areas of the farm for 90 days from the beginning of April but were separated into three groups of 10 for treatment. One group received a prophylactic regime of two injections of 20 mg/kg of a long-acting oxytetracycline on days 7 and 14 after introduction, one received a regime of three similar injections on days 7, 14 and 21 and the other group remained untreated prophylactically. The animals were observed early each morning in a crush, rectal temperatures being taken daily and blood smears when clinical signs of disease occurred. When clinical disease was confirmed in individual animals appropriate therapeutic treatment was implemented. In addition tick counts were made weekly. All untreated control animals required treatment for redwater between days 23 and 32 and eight of them then contracted heartwater of which five died despite therapy. Four animals from the group receiving two injections of oxytetracycline and one receiving three injections also contracted redwater but rather later. During the initial 35 day assessment period it was noticed that the majority of Boophilus ticks failed to engorge on the oxytetracycline-treated animals. In the second phase of the trial theileriosis (T. mutans-type) became evident in many animals and appeared to precipitate new or recrudescent clinical redwater and heartwater in several of them.(ABSTRACT TRUNCATED AT 250 WORDS)

Larvicidal properties against Ostertagia ostertagi of the faeces of calves treated with a sustained release formulation of morantel tartrate.

An experiment was carried out to assess the effect of morantel tartrate in the faeces of calves treated with a bolus on the survival and development of Ostertagia ostertagi eggs. Since the drug delivered from the bolus greatly reduces the nematode population in an infected animal and thus the number of eggs excreted it was necessary to mix O ostertagi eggs into the faeces of calves to which boluses had been administered. In three preliminary experiments it was shown that the methods used to extract the nematode eggs from faeces of infected cattle and remix them into faeces from uninfected cattle did not appear to affect their development into larvae or their even distribution in the faeces into which they had been remixed. The concentration of morantel tartrate lethal to O ostertagi eggs was in the range 0.0015 to 0.0025 M in vitro. It was demonstrated that the presence of the drug in the faeces of dosed calves prevented the maturation of approximately 99 per cent of O ostertagi eggs to infective larvae between days 7 and 84 after the administration of a bolus and of 75 per cent on day 91. These results help to explain the well recognised effect of the bolus in cleaning pastures of O ostertagi.

Development of a prophylactic regime using Terramycin/LA to assist in the introduction of susceptible cattle into heartwater endemic areas of Africa.

As a result of a personal survey in 1982, interviewing veterinarians from Louis Trichardt to Uitenhage, it was concluded that bovine heartwater is currently regarded as the most serious tick-borne disease problem in South Africa. A combination of long-acting oxytetracycline and prednisolone is regarded as the most effective therapy. The disease is almost inevitable in unprotected young high-grade susceptible stock introduced into endemic areas such as the northern Transvaal and the Valley Bushveld of Natal and the Eastern Cape. A series of trials was conducted at Settlers, Pietermaritzburg and East London on farms representative of these areas and it was demonstrated that 4 injections of 20 mg/kg of long-acting oxytetracycline on Days 0, 7, 14 and 21 after introduction enabled such stock to be introduced without the disease occurring. A further trial was carried out on the Pietermaritzburg farm, where it was shown that the number of injections could be reduced to 3, on Days 7, 14 and 21 or Days 7, 12 and 17, or even 2 on Days 7 and 14. Two points need stressing. First, these results were obtained in areas of high heartwater endemicity. Second, in order to be confident that the regimen will be effective it is necessary to have acquired knowledge of the epidemiology of the disease at the farm. Thus in the 2nd year at Pietermaritzburg we were able to use a reduced treatment regime we knew the pattern of disease occurrence.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigations on a Babesia isolated from Scottish sheep.

The pathognomic, serologic and morphometric identity of a Babesia sp. recently isolated from sheep in Argyllshire was studied. Initially, problems were encountered due to the occurrence of Eperythrozoon ovis as a contaminant of the isolate and treatment with neoarsphenamine failed to remove it. Finally, a combination of oxytetracycline therapy and rapid passage allowed isolation of the Babesia sp. and its preservation in the form of a glycerolized, infected blood stabilate. Inoculation of the stabilate into splenectomized sheep produced a mile non-pyrogenic disease. Serologically the parasite was seen to have no affinity with either of the two Babesia recognized as parasitizing sheep, but some affinity with the cattle parasite B. divergens. Morphometrically it was seen to have affinity with the deer parasite B. capreoli and with the Babesia sp. isolated from red deer in Scotland, and the low number of budding forms of the parasite seen suggested that the parasite might be reproducing slowly in an alien host. It was concluded that the parasite was likely to be B. capreoli derived from red deer via the tick Ixodes ricinus.

Investigations on Babesia motasi isolated from Wales.

A number of observations were carried out on the effect of the newly isolated parasite, Babesia motasi (Wales) on intact and splenectomised sheep and on a splenectomised goat. The parasite was not pathogenic for intact animals but caused fever and anaemia in splenectomised ones. B motasi (Wales) was also studied morphologically, morphometrically and serologically. The common form of the parasite was seen to be a double pyriform, the mean length of one side being 2.23 micrometer. It appeared to be morphometrically and serologically close to the other north European B motasi strains but distinct from B motasi (Turkey). In a limited serological survey, experience of infection with B motasi appeared to be common in sheep grazing in coastal areas of North Wales, but rare in a part of South Wales known to harbour the vector tick Haemaphysalis punctata. Transovarial transmission of B motasi by H punctata took place with facility.

Efficacy of imidocarb diproprionate and primaquine phosphate in the prevention of tick-borne disease in imported Hereford heifers in South Korea.

This paper describes the build-up of tick-borne blood parasites in a group of Hereford heifers imported from New Zealand to the island of Jeju Do, South Korea. All became infected with Theileria sergenti and half with Babesia bigemina. An attempt was made to contain the 2 parasites by treatment with either primaquine phosphate or imidocarb diproprionate. Both drugs had some prophylactic activity against T. sergenti for at least 26 days and imidocarb dipropionate eliminated B. bigemina. Since T. sergenti infections built up subsequently in the animals it is suggested that repeated prophylaxis combined with regular acaricide treatment of imported cattle is necessary to keep piroplasmosis under control.

Quinuronium sulphate for the treatment of Babesia divergens infections of splenectomised calves.

Quinuronium sulphate was inoculated into splenectomised calves at various times in relation to artificial infection of the calves with Babesia divergens. When the drug was given one day before the parasites it had no effect on the course of the infection. However, when it was given at the time of onset of fever or haemoglobinuria, development of the infection was arrested. Two weeks after therapy, recrudescences of parasites invariably occurred. In the case of animals treated at onset of fever these recrudescences were accompanied by increasing anaemia. Treated animals resisted subsequent challenge but remained as carriers of the parasite.

The use of imidocarb diproprionate for the treatment of Theileria sergenti infections of cattle.

Imidocarb diproprionate (IMDP) was used therapeutically at a dose of 1.2 mg IMDP/kg of body weight against Theileria sergenti infections in Hereford heifers on the island of Jeju-Do, Republic of Korea. In the first experiment IMDP was seen to be at least as effective in reducing T. sergenti parasitaemias as primaquine phosphate (primaquine), the drug normally used on the island. In the second and third experiments IMDP was shown to reduce T. sergenti parasitaemias by about 80%. No drug is known to be completely effective against T. sergenti infections but the suggestion is made that IMDP may be used in preference to primaquine for treatment of acutely ill animals since it also has the advantage of eliminating Babesia ovata, another element of the piroplasmosis syndrome on the island.

Field use of an irradiated blood vaccine to protect cattle against redwater (Babesia divergens infection) on a farm in Dorset.

A field trial was conducted in Dorset to determine whether calves could be protected against babesiosis by the prior inoculation of irradiated blood infected with Babesia divergens. The trial involved 99 Friesian heifers. Forty were inoculated with infected blood from a donor calf after the blood had been irradiated to a dose of 28 kilorads, 31 were immune animals which had grazed on the infected site the previous year and 28 were susceptible animals. After exposure on a hillside where there was a high risk of contracting the disease, 21 of 28 susceptible animals became clinically affected by redwater and required treatment whereas no animals in the other two groups were affected. It was shown that there was a 100 per cent risk of disease at the site and serological and haematological evidence corroborated the clinical results in demonstrating total protection of the vaccinated animals. Vaccination against redwater appears preferable to therapy, since vaccination before exposure on an infected pasture can replace frequent monitoring of the animals and subsequent therapy late in the course of the disease.

Babesia divergens: combination of dead and live parasites in an irradiated vaccine.

Two experiments were carried out to investigate the hypothesis that the protective effect of an irradiated Babesia divergens vaccine was due to the combined inoculation of large numbers of dead parasites and small number of live ones. In the first experiment it was demonstrated that animals receiving 10(8) parasites irradiated at 25 kilorads had more severe B divergens reactions than animals in a previous experiment which had received 10(10) parasites irradiated at 24, 28 or 32 kilorads. In the second experiment it was shown that the simultaneous inoculation of 10(10) parasites killed by irradiation at 50 kilorads and 10(8) parasites irradiated at 25 kilorads resulted in the suppression of the relatively severe reactions induced by inoculation of the 25 kilorad-irradiated parasites alone. It was also shown that the simultaneous inoculation of 10(10) parasites irradiated at 50 kilorads and 10(4) live parasites similarly suppressed the anticipated reactions of the calves. These results indicated that the hypothesis was correct under the conditions of the experiment.