28 April 2025

3 minute read

By: Chris Wright

Asia

Jesper Chia-Hui, University of Minnesota and colleagues in the US and the Philippines, presented the results of a study during the 2024 Leman Swine Conference.

The African swine fever (ASF) outbreak in Southeast Asia, following China in 2019, severely impacted the Philippines' swine industry for five years, causing substantial losses for farmers. The National African Swine Fever Prevention and Control Program (NASFPCP), launched in 2021, aims to combat ASF through surveillance, monitoring, and repopulation.

Batangas, a key hog-producing province, provided comprehensive ASF surveillance documentation. Data was collected from February 13, 2020, to December 21, 2021, by the Provincial Office of Batangas City, Philippines.

The repopulation protocol had three phases: (1) depopulation, cleaning, and disinfection; (2) downtime (20 days); and (3) introduction of sentinel animals (40 days). Data was analyzed to evaluate the effectiveness of the repopulation efforts across different variables. After total depopulation, diagnostic tests were done at various surveillance points.

In this study, 145 swine farms were analyzed, including 99 backyard farms and 46 commercial farms, with 10.1% and 8.7% testing positive at least once, respectively. Fourteen farms tested positive during the repopulation surveillance, necessitating immediate depopulation and re-entry into the surveillance process, while 90.34% (131/145) of the farms remained ASF-negative throughout the surveillance period.

Sensitivity and specificity varied across different testing days, with sensitivity notably increasing to 89% by day 27. The survival analysis of field samples shows both backyard and commercial farms have 90% negative detection rates, with overlapping 95% confidence intervals indicating no significant difference between them.

The ASF repopulation protocol demonstrated an overall success rate, with 90.34% of farms remaining ASF-negative. However, approximately 10% experienced protocol failure, highlighting the necessity for enhanced resources in less affluent municipalities or cities.

Sentinel animals on day 27 exhibited optimal sensitivity, suggesting potential implications for repopulation policies. Enhancing targeted surveillance is critical for improving early ASF detection and response.

ASF environmental impact

Rachel A. Schambow, University of Minnesota and colleagues in the US and the Philippines, presented the results of a study during the 2024 Leman Swine Conference.

Although ASF is well-recognized for its severe impact on trade and animal health, little research has focused on its environmental impacts from practices such as mass depopulation and carcass disposal. As they decompose, animal carcasses may pose pollution risks such as nitrogen, chemical and biological leachate components, and hazardous gases, which would be exacerbated at scales used for disease response.

Control activities for ASF could lead to risks in land, water, and air quality. ASF has also put endangered Philippine swine species at risk, such as the Bornean bearded pig, pygmy hog in India, and warty pigs of southeast Asia. However, the impact of ongoing global ASF outbreaks on environmental health is relatively unknown.

ASF has been present in the Philippines since 2019, and control efforts such as depopulation, carcass disposal, and movement controls have been applied. There is minimal relevant literature that directly addresses the environmental impacts of ASF, which indicates a significant research gap and underscores the need for future studies in this area.

An exploratory, qualitative systems in-person mapping exercise with a group of 18 private and public swine veterinarians was conducted in the Philippines in June 2024. The participants had extensive experience in prevention and response activities to ASF in the Philippines. The participants were first introduced to systems mapping, then split into three groups representing “pre-outbreak”, “immediate response,” and “endemic/long-term management” phases.

In small groups, they produced a rich picture map representing stakeholders and connections relevant to ASF’s environmental impact on the Philippines. The system map produced by the participants identified many important stakeholders that have decision-making power and impact on environmental health in the Philippines.

Concerns raised in this study included the threat of ASF to native endangered Visayan warty pigs and other swine species, and the potential for water contamination from carcass burial due to a high-water table.