Experimental infections of Babesia bigemina in American bison

Piroplasms in farmed American bison, Bison bison from Romania

The American bison (Bison bison) is the largest terrestrial mammal of North America, with around 350,000 individuals in the wild and in private herds but the knowledge regarding the presence of different vector-borne pathigens in these mammals is very poor. Babesia and Theileria spp. are tick-borne apicomplexan parasites which are considered to be among the most commonly found blood parasites of large ruminants, often with a high economic importance. However, the knowledge on piroplasms of bisons is extremely scarce. The aim of our study was to evaluate the presence of apicomplexan parasites in blood and tissues of farmed American bison from Romania. Overall, we tested 222 blood samples and 11 tissues samples (heart, liver, and spleen) from farmed B. bison raised for meat in Romania. All the samples were analyzed by nPCR targeting the 18SrRNA gene for piroplasmids. All positive samples were sequenced and analyzed phylogenetically. The overall prevalence of infection with piroplasmids in American bison was 1.65%, with Babesia divergens and Theileria sp. identified following sequencing. To our knowledge, this is the first report of piroplasms detected in blood and tissues of farmed B. bison from Europe. Further studies are necessary in order to obtain a better overview on the epidemiological status and clinical relevance of piroplasms in farmed American bisons.

Molecular Detection of Tick-Borne Pathogens in American Bison (Bison bison) at El Uno Ecological Reserve, Janos, Chihuahua, Mexico

American bison (Bison bison) is listed as near-threatened and in danger of extinction in Mexico. Recent studies have demonstrated the presence of several emerging pathogens at the Janos Biosphere Reserve (JBR), inhabited by one wild herd of American bison. Blood samples were collected from 26 American bison in the JBR. We tested for the presence of Anaplasma marginale, Babesia bigemina, B. bovis, Borrelia burgdorferi sensu lato, and Rickettsia rickettsii DNA using nested and semi-nested PCR protocols performing duplicates in two different laboratories. Results showed three animals (11.5%) positive for B. burgdorferi s. l., three more (11.5%) for Rickettsia rickettsii, and four (19.2%) for B. bovis. Two individuals were co-infected with B. burgdorferi s. l. and B. bovis. We found no animals positive for A. marginale and B. bigemina. This is the first report in America of R. rickettsii in American bison. American bison has been described as an important reservoir for pathogens of zoonotic and veterinary importance; thus, the presence of tick-borne pathogen DNA in the JBR American bison indicates the importance of continuous wildlife health surveys.

Experimental Infection of Ticks: An Essential Tool for the Analysis of Babesia Species Biology and Transmission

Babesiosis is one of the most important tick-borne diseases in veterinary health, impacting mainly cattle, equidae, and canidae, and limiting the development of livestock industries worldwide. In humans, babesiosis is considered to be an emerging disease mostly due to Babesia divergens in Europe and Babesia microti in America. Despite this importance, our knowledge of Babesia sp. transmission by ticks is incomplete. The complexity of vectorial systems involving the vector, vertebrate host, and pathogen, as well as the complex feeding biology of ticks, may be part of the reason for the existing gaps in our knowledge. Indeed, this complexity renders the implementation of experimental systems that are as close as possible to natural conditions and allowing the study of tick-host-parasite interactions, quite difficult. However, it is unlikely that the development of more effective and sustainable control measures against babesiosis will emerge unless significant progress can be made in understanding this tripartite relationship. The various methods used to date to achieve tick transmission of Babesia spp. of medical and veterinary importance under experimental conditions are reviewed and discussed here.

Babesiosis of wild carnivores and ungulates

Although large and small piroplasms have been reported from various wild carnivore and ungulate species, relatively few have been named. In the past, mere presence of a piroplasm in a specific host frequently prompted naming of a new species. Descriptions were often inadequate or lacking altogether. Currently, demarcation of species relies heavily on molecular characterisation. Even serological evidence is deemed insufficient. Experimental transmission of Babesia spp. from domestic to wild animals is usually only successful in closely related species, or after splenectomy. There are indications that endemic stability, similar to the situation in livestock, is the general pattern in Babesia sp. infections in wildlife. All lions in Kruger National Park were found to be infected with B. leo, which did not lead to clinical disease manifestation in artificially infected lions. Under stressful conditions, infections could flare up and be fatal, as purportedly happened to the famous lioness "Elsa". Similarly black rhinos, which can harbour Babesia bicornis without ill effects, may develop clinical babesiosis during confinement after capture. Zoo-bred animals, which were not exposed to Babesia spp. at a young age, may be fully susceptible when released into a natural environment where other members of their species occur. This could have major implications for ex situ conservation programmes aimed at bolstering natural wildlife populations.