Equine infectious anaemia and mechanical transmission: man and the wee beasties.
Abstract: There is no credible evidence that the lentivirus that causes equine infectious anaemia (EIA) replicates in invertebrates. The virus persistently infects its equid hosts and is often present in blood in significant quantities. Blood-feeding arthropods thus have the potential to transfer the virus between hosts, especially if their feeding on the first host is interrupted and immediately continued on a second host. The general details and dynamics of mechanical transmission are included in this paper, as this agent presents an excellent model. Mechanical transmission can be effectively controlled if the dynamics and interactions of the host, virus and vector populations are understood. Efficient transmission is proportional to the amount of agent found in the source material, the environmental survival of the agent, the number of vector feedings, the number of interrupted feedings, vector refeeding, the proximity of infected and naive hosts, host population density, and the length of time during which vectors and hosts are in contact. Establishing firm quantitative risk estimates for EIA is impossible, mainly because the virus content in blood can change exponentially from day to day. The EIA virus can be transmitted by horse flies for at least 30 minutes after feeding on a horse with acute signs of EIA, butthe probability of a horse fly being interrupted and completing its blood feeding on a second host at a distance of 50 m is very low, and the separation of infected and uninfected equids by 200 m breaks transmission. The statements above assume that human interactions are absent or do not contribute to the risk of virus transmission; however, the risk from human interventions, such as the too-often-used procedure of administering > 200 ml of plasma to foals, can easily be more than 10(7) times greater than the risk posed by a single horse fly. Controlling EIA depends upon the identification of persistently infected equids by serological testing because other methods of identifying infective virus orviral genetic material are less accurate or impractical.
Publication Date: 2015-11-26 PubMed ID: 26601453DOI: 10.20506/rst.34.2.2376Google Scholar: Lookup
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Summary
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The research paper discusses the dynamics of mechanical transmission of equine infectious anaemia (EIA), a lentivirus that infects horses persistently, and how understanding these dynamics can effectively control the transmission. Despite the lack of firm quantitative risk estimates due to day-to-day variations in virus content in blood, it provides insights on factors affecting efficient transmission and the role of human interventions in increasing the risk.
Mechanical Transmission of EIA
- EIA is a lentivirus that notably resides and multiplies within its equine hosts, commonly found in significant quantities within their blood.
- The virus isn’t known to replicate in invertebrates. However, blood-feeding arthropods, such as horse flies, can mechanically transfer the virus from one host to another, particularly when their feeding is disrupted on one host and immediately continued on a new, unaffected one.
Dynamics of Transmission
- The dynamics of transmission are complex and influenced by numerous factors, including the amount of virus in the source material, environmental survival of the agent, frequency of vector feedings, interrupted feedings and vector refeeding, proximity of affected and naive hosts, and the length of time vectors and hosts remain in contact. Understanding these dynamics can help develop cost-effective control measures.
- EIA virus can be transmitted by horse flies for at least 30 minutes after feeding on an infected horse.
- The paper also delineates the impracticality of typical transmission scenarios. For instance, the chance of a horse fly being disrupted and completing its feeding on another host 50 metres away is quite low. A separation of 200 meters between infected and uninfected horses can halt the transmission.
Role of Human Interventions
- Although the focus remains largely on vector-borne transmission, the research also underlines the role of human interventions in virus transmission.
- Practices like administering large volumes of plasma to foals greatly amplify the risk, arguably even more so than a single horse fly.
- The critical lever for limiting EIA spread lies in identifying persistently infected horses through serological testing, as other identification methods for infective virus or viral genetic material prove less accurate or impractical.
As an overarching conclusion, the study points out the importance of understanding the dynamics and interactions between the host, virus, and vector populations to effectively manage and control EIA.
Cite This Article
APA
Issel CJ, Foil LD.
(2015).
Equine infectious anaemia and mechanical transmission: man and the wee beasties.
Rev Sci Tech, 34(2), 513-523.
https://doi.org/10.20506/rst.34.2.2376 Publication
Researcher Affiliations
MeSH Terms
- Animals
- Culicidae / virology
- Diptera / virology
- Equine Infectious Anemia / transmission
- Horses
- Humans
- Infectious Anemia Virus, Equine / physiology
- Insect Vectors / virology
Citations
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- Cardenas NC, Sanchez F, Lopes FPN, Machado G. Coupling spatial statistics with social network analysis to estimate distinct risk areas of disease circulation to improve risk-based surveillance. Transbound Emerg Dis 2022 Sep;69(5):e2757-e2768.
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