Assessment of a low virulence Australian isolate of Anaplasma marginale for pathogenicity, immunogenicity and transmissibility by Boophilus microplus.

A 14-year-old cow (Dawn) born and kept in a Boophilus microplus-free region gave birth to a calf, which showed the presence of an Anaplasma marginale infection after splenectomy. The calf's grand dam was from a B. microplus infected area and we assume the infection originated via the transplacental route over two generations.

Overcoming constraints to meeting increased demand for Babesia bigemina vaccine in Australia.

Demand for live trivalent tick fever vaccine containing Babesia bovis, Babesia bigemina and Anaplasma centrale produced by the Department of Primary Industries, Queensland, has increased from less than 10,000 doses in 1988 to 500,000 doses in 2001. This paper describes a series of trials aimed at overcoming certain constraints to obtain B. bigemina parasitised erythrocytes (PEs) on a large enough scale from infected splenectomised calves to meet the demand.

Babesia bovis: culture of laboratory-adapted parasite lines and clinical isolates in a chemically defined medium.

Babesiosis caused by Babesia spp. is a disease of both veterinary and human importance. Here, we describe a method to continuously culture laboratory lines and field isolates of Babesia bovis in vitro in a chemically defined medium using (ALBU)MAX II as an alternative to bovine serum.

Immunity following use of Australian tick fever vaccine: a review of the evidence.

Objective: To review the evidence available on the degree and duration of immunity provided by Australian tick fever vaccines against Babesia bovis, B. bigemina and Anaplasma marginale infections in Australia and overseas.

Background: Vaccines containing attenuated strains of B bovis and B bigemina as well as A.

Vaccination against bovine babesiosis.

Bovine babesiosis is an important disease caused by Babesia bovis, B. bigemina, and B. divergens.

Application of PCR assays to determine the genotype of Babesia bovis parasites isolated from cattle with clinical babesiosis soon after vaccination against tick fever.

Objective: To demonstrate the value of PCR assays to determine the genotypes of Babesia bovis in cattle with clinical signs of babesiosis within 3 weeks after vaccination against tick fever.

Design: Samples from 5 cases of babesiosis in cattle soon after vaccination against tick fever were analysed in two PCR assays.

Procedure: Parasite DNA was purified from blood taken from cattle with signs of babesiosis within 3 weeks of vaccination against tick fever.

Effect of breed of cattle on innate resistance to infection with Anaplasma marginale transmitted by Boophilus microplus.

Objective: To assess the innate resistance of and transmission in naive Bos taurus cross Bos indicus and purebred Bos indicus cattle when placed in a paddock with cattle infected with Anaplasma marginale and carrying Boophilus microplus ticks.

Design: A group of 49 purebred B indicus, and 48 B indicus cross B taurus (50%, F1 generation) 24-month-old steers were kept in the same paddock with cattle artificially infected with a virulent isolate of A marginale and Boophilus microplus. The cattle were seronegative for A marginale at the start of the trial but had previously been exposed to Babesia bovis and B bigemina.

Transmission of Babesia spp by the cattle tick (Boophilus microplus) to cattle treated with injectable or pour-on formulations of ivermectin and moxidectin.

Objective: To assess the efficacy of ivermectin and moxidectin to prevent transmission of Babesia bovis and Babesia bigemina by Boophilus microplus to cattle under conditions of relatively intense experimental challenge.

Design: Naive Bos taurus calves were treated with either pour-on or injectable formulations of either ivermectin or moxidectin and then exposed to larvae of B microplus infected with B bovis or larvae or adults of B microplus infected with B bigemina. One calf was used for each combination of haemoparasite, B microplus life stage, drug and application route.

Effect of breed of cattle on transmission rate and innate resistance to infection with Babesia bovis and B bigemina transmitted by Boophilus microplus.

Objective: To assess the effect of breed of cattle on the transmission rates of and innate resistance to Babesia bovis and B bigemina parasites transmitted by Boophilus microplus ticks.

Design: Groups of 56 purebred B indicus and 52 B indicus cross B taurus (50%, F1 generation) steers were placed in a paddock seeded with and also naturally infested with B microplus which were the progeny of females ticks fed on B taurus cattle specifically infected with a virulent isolate of B bovis. The cattle were placed in the infested paddock 50 days after seeding had started.

Detection of calves persistently infected with bovine pestivirus in a sample of dairy calves in south-eastern Queensland.

Objective: To determine the proportion and incidence of calves persistently infected with bovine pestivirus in calves (n = 1521) supplied to the Tick Fever Research Centre and to assess the test regime to detect calves persistently infected with bovine pestivirus.

Design: Calves, 1 to 6 weeks old, selected for use in the production of the tick fever vaccine were collected from 21 properties in 56 separate groups between October 1990 and December 1996. Each group was examined for the presence of calves persistently infected with bovine pestivirus.

Effect of breed of cattle on innate resistance to infection with Babesia bovis, B bigemina and Anaplasma marginale.

Objective: To assess the innate resistance of naive Bos taurus, Bos taurus cross Bos indicus and Bos indicus cattle to virulent Babesia bovis, B bigemina and Anaplasma marginale parasites.

Design: Groups of 10, pure B indicus, 1/2 B indicus cross, 1/4 B indicus cross and pure B taurus steers were infected with virulent B bovis, B bigemina and A marginale parasites [corrected].

Procedure: Sequential infections were carried out by intravenous inoculation of infected blood containing 1 x 10(8) parasites of B bovis, followed by B bigemina and then A marginale.

Studies on failure of T strain live Babesia bovis vaccine.

Field investigations of the protection afforded by the Australian live Babesia bovis vaccine used in the early 1990s (T strain) revealed inadequate vaccine-induced protection in certain herds. Vaccination/challenge trials using 207 experimental cattle were conducted to evaluate the protection afforded by T strain B bovis against field isolates from these herds. The trials investigated whether isolates that could 'break-through' T strain immunity were present in the field, the ability or inability of specific cattle to develop protective immunity after vaccination with T strain and the effect of attenuation and maintenance procedures on the immunogenicity of T strain.

A survey of cattle producers in the Boophilus microplus endemic area of Queensland to determine attitudes to the control of and vaccination against tick fever.

A survey by mail was used to determine the views of beef producers in the Boophilus microplus endemic area of Queensland on the control of and vaccination against tick fever. Data from 448 questionnaires were analysed, representing 2.7% of beef producers in the survey area.

Use of in vitro culture to isolate Babesia bovis from Theileria buffeli, Eperythrozoon wenyoni and Anaplasma spp.

On nine separate occasions, Babesia bovis microaerophilus stationary phase (MASP) cultures were initiated with blood from calves with concurrent infections of B. bovis and Theileria buffeli, Eperythrozoon wenyoni or Anaplasma spp. In each case B.

Investigations of breakdowns in protection provided by living Babesia bovis vaccine.

Field investigations of protection afforded by live Babesia bovis vaccine in Australia revealed that a ninefold increase in vaccine failures occurred in the period from 1985 to 1990. Laboratory trials using 189 experimental cattle were conducted to evaluate the protection afforded by the Babesia bovis strain used in the commercial vaccine during this time. Four isolates from clinical cases of babesiosis in vaccinated cattle were assessed.

Prevalence of Babesia bovis and Anaplasma marginale at selected localities in Sri Lanka.

Sera were collected from a minimum of 20 cattle aged nine to 36 months at each of 14 localities in five climatic zones of Sri Lanka. Sera were tested for antibodies to Babesia bovis and Anaplasma by an indirect fluorescent antibody test and a card agglutination test, respectively. Antibodies to B.

Growth of Babesia bigemina parasites in suspension cultures for vaccine production.

An Australian Babesia bigemina vaccine strain was maintained in suspension culture for 40 days. Parasite growth was compared using two tissue-culture flask sizes (25 and 75 cm2), four gas mixes (2%, 2.5%, 3% and 3.

Study of virulence and vector transmission of Babesia bovis by use of cloned parasite lines.

Cloned lines of Babesia bovis were prepared from the avirulent vaccine strain, Ka, by an in vivo limiting dilution procedure. The virulence of these clones for adult Bos taurus cattle varied from completely avirulent to highly virulent. This suggests that the parent strain, Ka, is composed of a mixture of subpopulations of varied virulence.

Methods currently used for the control of anaplasmosis and babesiosis: their validity and proposals for future control strategies.

Four alternative approaches to the control of anaplasmosis and babesiosis as a complex of diseases are identified: no active control, tick control, immunization, and chemoprophylaxis. These methods may be utilized in one of five strategies: tick eradication with or without concurrent immunization, tick reduction with or without concurrent immunization or no active control. Factors influencing the choice of strategy are discussed.

Growth of Babesia bovis parasites in stationary and suspension cultures and their use in experimental vaccination of cattle.

A combination of stationary culture and suspension culture was used to produce litre quantities of Babesia bovis parasites suitable for use as live vaccine. The Australian vaccine strain of B bovis, Ka, was maintained continuously in microaerophilus stationary phase (MASP) cultures, and for a short period in batch and flow-through spinner flask cultures. Although continuous culturing was not achieved in spinner flasks, the production of litre quantities of heavily parasitised erythrocytes was achieved more simply than by using MASP cultures.

Infectivity of cryopreserved Babesia bovis, Babesia bigemina and Anaplasma centrale for cattle after thawing, dilution and incubation at 30 degrees C.

Blood containing either Babesia bovis, Babesia bigemina or Anaplasma centrale was mixed with an equal volume of 3 M glycerol in phosphate-buffered saline with or without glucose and then stored in liquid nitrogen for 2-30 days. After being thawed, the parasitized blood was subjected to various procedures, including dilution up to 1000-fold followed by incubation at 30 or 4 degrees C for 8 h, before infectivity of the parasites was tested in a total of 70 cattle. The results showed that the blood cryopreserved with glycerol remained highly infective after thawing, despite dilution and incubation for 8 h at 30 degrees C.