The Viremic Phase and Humoral Immune Response Against African Horse Sickness Virus That Emerged in Thailand in 2020.
Abstract: African horse sickness (AHS), a life-threatening disease caused by African horse sickness virus serotype 1 (AHSV-1), emerged in Thailand in February 2020 with 607 cases and a 93% fatality rate. The outbreak was mitigated by vector control and a live attenuated virus (LAV) vaccine. Information regarding viremia and immunity after infection and vaccination during outbreaks are essential for controlling disease transmission. This study evaluated these parameters in 15 infected naïve horses and 11 vaccinated horses during the 2020 outbreak. Whole blood was collected and subjected to RT real-time PCR to detect viremia up to 52 weeks post-infection. ASHV-specific antibodies were accessed by blocking ELISA until 37 weeks post-vaccination. In both groups, viremia appeared in the first week and lasted until week 5 in 25% of the horses. Moreover, seroconversion occurred at week 5 in 73.3% of infected horses and at week 3 in 90% of vaccinated horses. Antibodies persisted in both groups until the end of study, with more uniform levels in vaccinated animals. Chronological relations among clinical signs, viremia, and immunity were analyzed. These findings support the use of insect-proof housing for horses for at least 5 weeks after exposure or vaccination, and provide essential insights into AHSV epidemiology and control.
Publication Date: 2025-09-11 PubMed ID: 41012803PubMed Central: PMC12474096DOI: 10.3390/vetsci12090878Google Scholar: Lookup
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- Journal Article
Summary
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Overview
- This study evaluated the presence of African horse sickness virus (AHSV) in the bloodstream (viremia) and the antibody (humoral) immune responses in horses naturally infected or vaccinated during the 2020 AHS outbreak in Thailand.
- The research aimed to understand the timeline of virus presence and antibody development to inform control measures against the disease.
Background
- African horse sickness (AHS): A severe and often fatal disease in horses caused by the African horse sickness virus serotype 1 (AHSV-1).
- 2020 Thailand outbreak: Emerged with 607 cases and a very high fatality rate of 93%, indicating a severe epidemic.
- Control measures: Included vector control (reducing insect vectors) and vaccination using a live attenuated virus (LAV) vaccine.
- Importance of study: Knowledge about how long the virus stays in the blood and how the immune response develops in infected and vaccinated animals is crucial for managing AHS transmission.
Study Design and Methods
- Subjects: 15 horses infected with AHSV-1 who had no prior immunity (naïve) and 11 horses vaccinated with the LAV during the 2020 outbreak.
- Sampling: Whole blood was collected from these horses over time to monitor virus presence and immune response.
- Viremia detection: Used real-time reverse transcriptase PCR (RT real-time PCR) to detect viral RNA in blood samples, tracking viremia up to 52 weeks post-infection.
- Antibody detection: ASHV-specific antibodies were measured by blocking ELISA until 37 weeks post-vaccination to assess the humoral immune response.
Key Findings on Viremia
- Viremia was detectable in both infected and vaccinated horses starting in the first week after exposure or vaccination.
- This viremia lasted until about week 5 in approximately 25% of horses, indicating that some horses had virus circulating in their blood for over a month.
Key Findings on Immune Response
- Seroconversion timing:
- Occurred at week 5 in 73.3% of infected horses, showing that most developed detectable antibodies five weeks after infection.
- Occurred earlier, by week 3, in 90% of vaccinated horses, indicating a quicker immune response post-vaccination.
- Antibody persistence:
- Antibodies remained present in both groups until the end of the study (up to 37 weeks post-vaccination/infection).
- Vaccinated horses showed more uniform antibody levels, suggesting consistent immunity conferred by the LAV vaccine.
Chronological Relationship Among Clinical Signs, Viremia, and Immunity
- By correlating when clinical symptoms appeared, the presence of virus in blood, and antibody levels, researchers gained insights into disease progression.
- Understanding this timeline helps identify critical periods when the horses are infectious and when they develop immune protection.
Implications for Disease Control
- Findings suggest horses should be kept in insect-proof housing for at least 5 weeks after exposure or vaccination to prevent transmission through insect vectors during the viremic period.
- Knowledge of antibody development timing supports vaccination strategies by highlighting when protection is expected to develop.
- The study contributes valuable data for epidemiological modeling and designing effective AHS control programs in endemic or outbreak settings.
Cite This Article
APA
Pipitpornsirikul P, Thangthamniyom N, Laikul A, Songkasupa T, Pathomsakulwong W, Apichaimongkonkun T, Kasemsuwan S, E-Kobon T, Lekcharoensuk P.
(2025).
The Viremic Phase and Humoral Immune Response Against African Horse Sickness Virus That Emerged in Thailand in 2020.
Vet Sci, 12(9), 878.
https://doi.org/10.3390/vetsci12090878 Publication
Researcher Affiliations
- Center for Agricultural Biotechnology, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom 73140, Thailand.
- Center of Excellence on Agricultural Biotechnology: (AG-BIO/MHESI), Bangkok 10900, Thailand.
- Department of Microbiology and Immunology, Faculty of Veterinary Medicine, Kasetsart University, Bangkhen Campus, Bangkok 10900, Thailand.
- Department of Large Animal and Wildlife Clinical Science, Faculty of Veterinary Medicine, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom 73140, Thailand.
- Virology Section, National Institute of Animal Health, Department of Livestock Development, Bangkok 10900, Thailand.
- Equine Clinic, Kasetsart University Veterinary Teaching Hospital, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom 73140, Thailand.
- Equine Clinic, Kasetsart University Veterinary Teaching Hospital, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom 73140, Thailand.
- Department of Veterinary Public Health, Faculty of Veterinary Medicine, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom 73140, Thailand.
- Department of Genetics, Faculty of Science, Kasetsart University, Bangkhen Campus, Bangkok 10900, Thailand.
- Department of Microbiology and Immunology, Faculty of Veterinary Medicine, Kasetsart University, Bangkhen Campus, Bangkok 10900, Thailand.
Grant Funding
- N42A670624 / the National Research Council of Thailand (NRCT) and Kasetsart University (KU) under the Thailand Science Research and Innovation (TSRI)
- CRP6705031590 / Agricultural Research Development Agency (ARDA)
- FF(KU)7.68 / Kasetsart University Research and Development Institute (KURD)
Conflict of Interest Statement
The authors declare no conflicts of interest.
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