[Babesiosis in dogs in the Netherlands (author's transl)]

In recent years, babesiosis is frequently observed in dogs which have been on holiday with their owners in southern Europe. The epidemiology and wide variety of symptoms are discussed. Satisfactory results were obtained on treatment with Berenil (Hoechst) and Acaprin (Bayer). In addition to tick control, Imizole (Burroughs Wellcome) might be adopted in preventive treatment.

A note on the transmission of Babesia bovis (syn B argentina) by the one-host tick, Boophilus microplus

Boophilus microplus infected with Babesia bovis were transferred artificially from one splenectomised calf to another during each moult in the parasitic life cycle of the tick. Eggs from the engorged female ticks recovered at the end of the cycle were incubated and the resulting larvae used to infest more splenectomised calves. Babesia bovis was transmitted only by the original larvae used at the commencement of the experiment and it was concluded that the protozoan parasite did not persist in an infective form in the ticks beyond the larval stage.

Intraerythrocytic parasitosis in humans with Entopolypoides species (family Babesiidae). Association with hepatic dysfunction and serum factors inhibiting lymphocyte response to phytohemagglutinin

We have observed two cases of human infection with intraerythrocytic protozoa. The organisms appeared to be in the Entopolypoides group, which had not previously been associated with human infection. One patient was asplenic. Both patients had hepatic dysfunction, and their serum samples contained blocking factors that interfered in vitro with the stimulation of normal lymphocytes by phytohemagglutinin. It appears that in humans, as well as in experimental animals, host factors are important in resistance to infection by intraerythrocytic parasites. These factors include the presence of a spleen and cell-mediated and humoral immunities. Possibly similar infections will be observed in patients with other impairments of T-cell function, such as those induced by malignancy, thymic dysfunction, or immunosuppressive drugs.

Bovine babesiosis: severity and reproducibility of Babesia bovis infections induced by Boophilus microplus under laboratory conditions

A total of 61 intact Holstein-Friesian calves were exposed to Babesia bovis (= B argentina) by the injection of infected blood or the application of infected Boophilus microplus larvae. Tick-induced infections were uniformly severe, even when induced by relatively small numbers of infected ticks. In contrast, calves infected with carrier blood experienced mild, subclinical reactions despite detectable parasitaemia. The greater severity of tick-induced reactions appeared to be due to the large number of infective doses injected by each infected tick rather than greater virulence of tick versus blood-origin babesiae. The severity of tick-induced babesiosis was related to the age of the experimental calves, with more severe reactions and high mortality occurring among older animals. The mean daily temperature rise increased with age and was highest in 15 animals dying of babesiosis. No relationship could be found between peripheral blood parasitaemia, packed cell volume reduction and mortality in tick-induced infections. One thousand larvae from infected colonies induced babesiosis in all of 29 animals exposed. Although larval transmission of B bovis is difficult to quantitate, there would seem to be no objection to using a controlled tick-borne challenge in the laboratory for assessment of susceptibility.

The identification of Babesia equi in Australia

A Babesia parasite, isolated from the blood of a horse at Bowral, New South Wales, was identified on the basis of its morphological features, host specificity and serological reactions, as Babesia equi (Laveran 1901). The case was originally reported by Churchill and Best (1976, Aust. vet. J. 52: 487) and is the first record of equine babesiosis in Australia. In preliminary studies, the organism produced only a mild disease in an intact horse, but caused the typical clinical syndrome of acute babesiosis in a splenectomised horse, which died 19 days after the intravenous inoculation of the parasites.

Failure of vaccine strains of Babesia bovis to regain infectivity for ticks during long-standing infections in cattle

Two strains of Babesia bovis that were known to have lost infectivity for the normal tick vector, Boophilus microplus, due to repeated blood passaging in cattle, were studied to determine whether the strains would regain infectivity for ticks during longstanding infections. Parasitaemias were monitored in 4 chronically infected calves that were regularly infested with ticks. Two strains of ticks known to be susceptible to infection with unmodified strains of B. bovis were used. Adult female ticks that dropped from the calves on days that a parasitaemia was evident were tested for B. bovis infection. Sixty-six batches of ticks collected up to 279 days after infection of the calves produced 14 pools of larvae, none of which transmitted infection. Primary infections established from the chronic infections by subinoculation at 200, 259 and 333 days after infection of the calves were also not transmitted by ticks.

Experimental transmission of Babesia major by Haemaphysalis punctata

Using a newly isolated strain of Babesia major and a clean strain of laboratory reared Haemaphysalis punctata it was shown that adult female ticks could be alimentarily infected by feeding on infected calves but that larvae and nymphae could not. All stages were able to transmit the parasite. Two syringe passages of B major resulted in a complete loss of infectivity to ticks.

Babesia bigemina in Kenya: experimental transmission by Boophilus decoloratus and the production of tick-derived stabilates

A Babesia-free batch of laboratory reared Boophilus decoloratus ticks was infected with a Kenyan strain of Babesia bigemina by feeding them on a steer infected by inoculation of a blood stabilate. The engorged female ticks showed developing stages of B. bigemina in their haemolymph and subsequently their progeny transmitted the parasite to a susceptible splenectomized steer. Attempts were made to produce stabilates from pre-fed larvae and nymphs derived from infected batches of B. decoloratus. Only the stabilates derived from the nymphs pre-fed either on cattle or rabbits produced B. bigemina infection when inoculated intravenously into susceptible cattle.

Human babesiosis on Nantucket Island: transmission by nymphal Ixodes ticks

In order to identify potential vectors of human babesiosis (Babesia microli) in southern Massachusetts, I attempted to transmit the infection via nymphal ticks of that species found to be most abundant on reservoir hosts (Peromyscus leucopus) in nature. Mice were collected at frequent intervals throughout a year in a known enzootic focus on Nantucket Island, and ticks were removed by hand. Ticks of only two species were present; larvae and nymphs of Ixodes scapularis were about 10 times as numerous as were those of Dermacentor variabilis. Accordingly, I. scapularis were used in attempts to transmit a strain of Babesia derived from a human infection recently acquired near the study site. Larvae were permitted to feed on an infected hamster and nymphs derived from these larvae were placed on each of 11 non-infected hamsters. All but one hamster became infected. Nymphs reared from larvae that had attached to a non-infected hamster did not transmit babesiosis to other hamsters. These results suggest that I. scapularis serves as a vector of babesios-s on Nantucket hamsters. These results suggest that I. scapularis serves as a vector of babesiosis on Nantucket Island.

Infection rates and outbreaks of disease due to Babesia argentina in unvaccinated cattle on 5 beef properties in south-eastern Queensland

Serums from unvaccinated groups in 5 herds of beef-cattle in South-East Queensland were tested for antibodies to Babesia argentina at intervals while the cattle were increasing in age from about 6 months. An indirect fluorescent antibody test was used. Infection rates, indicating the proportions of the groups that had been exposed to tick-transmitted infection were 49.2, 56.9 and 69.1% for cattle aged approximately 6, 12 and 18 months, respectively. The degree to which cattle were infested with the vector, Boophilus microplus, was estimated. There appeared to be a strong correlation between infection rate and tick incidence. Four serologically negative animals died of either confirmed or suspected babesiosis during the sampling period. Sickness was observed in 5 others. The serological status of 57 changes from negative to positive without symptoms being observed, indicating relatively low mortality and morbidity rates in the enzootic situation studied.

Human babesiosis: reservoir in infection on Nantucket Island

Examination of blood films from six species of rodents and lagomorphs on Nantucket Island disclosed infections with Babesia microti in all of five Microtus pennsylvanicus (field mice) and 31 of 39 Peromyscus leucopus (white-footed or deer mice). Six human cases of clinical babesiosis have recently been diagnosed on the island.

Piroplasmosis in buffaloes and its serological diagnosis based on a homology between buffalo and bovine immunoglobulins

Babesia argentina, Babesia bigemina and Theileria mutans were transmitted experimentally from water buffaloes (Bubalus bubalis) to splenectomised Bos taurus calves. Buffaloes were positive to an indirect fluorescent antibody test for B. argentina when reagents of bovine origin were used. The formation of similar patterns during immunoelectrophoresis suggested a homology of buffalo and bovine serum proteins, particularly IgG.