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An emerging parasitic disease has been identified in the United Kingdom for the first time. Babesia venatorum has historically been reported in animal and human populations throughout other parts of Europe and China, however, a recent study has confirmed the presence of the parasite in sheep in Scotland [1]. This has led to concerns regarding the spread of the disease, infection in domestic animals, and future containment.
BACKGROUND
Babesia venatorum, also referred to as Babesia sp. EU1, is part of a larger group of about 100 protozoan parasites transmitted by Ixodes ricinus ticks. Of the 100 species, only about 5 cause disease in humans, known as babesiosis [2]. Since 2003, when the parasite was first given the name B. venatorum, reports have been increasing, with 49 human cases in China, 3 in Europe (Italy and Austria), and identification of the parasite in ticks in the Czech Republic [3,4]. These reports, though increasing, most likely do not reflect the actual geographic spread or disease burden. Currently, there is not enough testing on humans and ticks to identify the parasite, and tickborne diseases are often difficult and complex overall, both of which contribute to the under-reporting of this disease [5].
DISEASE
Babesisosis as previously understood, is most severe in individuals with immune suppression, resulting in malaria-like clinical presentation including the destruction of red blood cells, anemia, low platelet count, destruction of vital organs, and death [6]. The most concerning aspect of the reported spread of B. venatorum specifically is its ability to infect healthy individuals. A case series in China reported, of the individuals with B. venatorum, 66% had fever, 41% had headache and 29% had elevated bilirubin [2]. Due to the recent emergence and low reported cases, there is not extensive information regarding treatment for B. venatorum. Babesiosis overall is quite treatable if it is caught early on. However, due to the rare nature, cross-reactivity with other strains, and lack of knowledge of these types of diseases, timely identification and diagnosis is very difficult [1].
STUDY FINDINGS
The study that reported presence of the parasite found that 12% of the 93 sheep tested were positive for B. venatorum on 2 farms in Northeast Scotland [1]. Since the parasite had previously never been found in sheep or in the United Kingdom, this begs the question what other animals could be hosts, and how did the parasite get to Scotland? The researchers speculate that it may have been transported by bird species, which have been shown to carry infected ticks long distances [7]. Where else could the infected ticks migrate to? The answer really lies in where they can survive.
NEXT STEPS
Improved testing is needed to actually begin conducting effective surveillance of B. venatorum. With better diagnostics, we will be able to identify the true burden of this novel potential threat in animal and human populations. Knowing which animals are hosts of the parasite will allow us to implement control programs to prevent the spread (e.g. restriction of sheep and cattle transportation), create best practices for diagnosis, and develop effective treatments.
Sources:
[1]: https://wwwnc.cdc.gov/eid/article/25/12/19-0459_article#r2
[2]: https://academic.oup.com/cid/article/67/7/1110/4925749
[3]: https://www.ncbi.nlm.nih.gov/pubmed/26094510
[4]: https://wwwnc.cdc.gov/eid/article/9/8/02-0748_article
[5]: https://www.ncbi.nlm.nih.gov/pubmed?cmd=Retrieve&db=PubMed&list_uids=24104943&dopt=Abstract
[6]: https://www.cdc.gov/parasites/babesiosis/disease.html
[7]: https://www.ncbi.nlm.nih.gov/pubmed?cmd=Retrieve&db=PubMed&list_uids=21699719&dopt=Abstract
[8]: https://www.ncbi.nlm.nih.gov/pubmed?cmd=Retrieve&db=PubMed&list_uids=25636942&dopt=Abstract
