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Assessment of a low virulence Australian isolate of Anaplasma marginale for pathogenicity, immunogenicity and
Russell E Bock1, Albertus J deVos, Terry G Kingston
1Tick Fever Research Centre, Department of Primary Industries, Queensland, 280 Grindle Road, Wacol, Queensland 4076, Australia. russell.bock@dpi.qld.gov.au
Abstract:
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. An isolate, prepared from the calf, had similar or lower pathogenicity as Anaplasma centrale, and previously exposed steers were resistant to challenge by four A. marginale field isolates. Two attempts to transmit the isolate using B. microplus were unsuccessful. Our results indicate that Dawn A. marginale may be a useful vaccine in Australia and warrants larger scale validation of its safety and potency locally as well as of the protection it affords against African and New World isolates.
Insights
A novel Anaplasma marginale isolate from a calf, potentially transmitted transplacentally over two generations, showed low pathogenicity. This Anaplasma marginale isolate may be a promising candidate for a cattle vaccine in Australia.
Area of Science:
- Veterinary Medicine
- Parasitology
- Animal Health
Background:
- Anaplasma marginale causes significant economic losses in cattle globally.
- Transplacental transmission of Anaplasma marginale is a potential, albeit less common, route of infection.
- The development of effective vaccines is crucial for controlling anaplasmosis.
Purpose of the Study:
- To characterize a novel Anaplasma marginale isolate from a calf born in a Boophilus microplus-free region.
- To assess the pathogenicity and potential vaccine suitability of this Anaplasma marginale isolate.
- To evaluate cross-protection against other Anaplasma marginale field isolates.
Main Methods:
- A calf born in a B. microplus-free area developed Anaplasma marginale infection.
- An isolate was prepared from the infected calf and its pathogenicity was compared to Anaplasma centrale.
- Steers previously exposed to Anaplasma marginale were challenged with field isolates.
- Attempts were made to transmit the isolate using B. microplus.
Main Results:
- The Anaplasma marginale isolate exhibited similar or lower pathogenicity compared to Anaplasma centrale.
- Previously exposed steers demonstrated resistance to challenge by four A. marginale field isolates.
- Two attempts to transmit the isolate via B. microplus were unsuccessful, suggesting limited tick transmission capability.
Conclusions:
- The Dawn Anaplasma marginale isolate shows potential as a vaccine candidate for cattle in Australia.
- Further large-scale validation of the vaccine's safety, potency, and efficacy against diverse isolates is warranted.
- The isolate's low pathogenicity and potential for cross-protection make it a valuable subject for anaplasmosis control research.
