Evidence for exposure of asymptomatic domestic pigs to African swine fever virus during an inter-epidemic period in Zambia
- 1 November 2020
- journal article
- research article
- Published by Hindawi Limited in Transboundary and Emerging Diseases
- Vol. 67 (6), 2741-2752
- https://doi.org/10.1111/tbed.13630
Abstract
African swine fever (ASF) causes persistent outbreaks in endemic and non-endemic regions in Zambia. However, the epidemiology of the disease is poorly understood, particularly during the inter-epidemic periods. We conducted surveillance for ASF in asymptomatic domestic pigs and soft ticks in selected Zambian provinces. While serum samples (n = 1,134) were collected from crossbred pigs from all study sites between 2014 and 2017, whole blood (n = 300) was collected from both crossbred and indigenous pigs in Eastern Province (EP) in 2017. Soft ticks were collected from Mosi-oa-Tunya National Park in Southern Province (SP) in 2019. Sera were screened for antibodies against ASF by ELISA while genome detection in whole blood and soft ticks was conducted by PCR. Ticks were identified morphologically and by phylogenetic analysis of the 16S rRNA gene. Seroprevalence was highest in EP (50.9%, 95% CI [47.0-54.9]) compared to significantly lower rates in SP (2.9%, 95% CI [1.6-5.1]). No antibodies to ASFV were detected in Lusaka Province. In EP, the prevalence of ASFV genome was 11.7% (35/300), significantly higher (OR = 6.2, 95% CI [2.4-16.6]) in indigenous pigs compared to crossbred pigs. The pooled prevalence of ASFV genome in ticks was 11.0%, 95% CI [8.5-13.9]. Free-range husbandry system was the only factor that was significantly associated with seropositive (p < .0001, OR = 39.3) and PCR-positive results (p < .001, OR = 5.7). Phylogenetically, based on the p72 gene, ASFV from Ornithodoros moubata ticks detected in this study belonged to genotype I, but they separated into two distinct clusters. Besides confirming ASF endemicity in EP and the presence of ASFV-infected ticks in SP, these results provide evidence for exposure of domestic pigs to ASFV in non-endemic regions during the inter-epidemic period.This publication has 34 references indexed in Scilit:
- Phylogeographic Analysis of African Swine Fever Virus, Western Europe, 2018Emerging Infectious Diseases, 2019
- Taenia solium control in Zambia: The potholed road to successParasite Epidemiology and Control, 2018
- Detection of African swine fever virus in the tissues of asymptomatic pigs in smallholder farming systems along the Kenya–Uganda border: implications for transmission in endemic areas and ASF surveillance in East AfricaJournal of General Virology, 2017
- Prevalence of African swine fever virus in apparently healthy domestic pigs in UgandaBMC Veterinary Research, 2013
- African swine fever virus replication and genomicsVirus Research, 2013
- African swine fever in the North Caucasus region and the Russian Federation in years 2007–2012Virus Research, 2013
- Development of a nested PCR and its internal control for the detection of African swine fever virus (ASFV) in Ornithodoros erraticusArchiv für die gesamte Virusforschung, 2005
- Highly Sensitive PCR Assay for Routine Diagnosis of African Swine Fever Virus in Clinical SamplesJournal of Clinical Microbiology, 2003
- Phylogeny of hard- and soft-tick taxa (Acari: Ixodida) based on mitochondrial 16S rDNA sequences.Proceedings of the National Academy of Sciences of the United States of America, 1994
- Genetic Diversity of African Swine Fever Virus Isolates from Soft Ticks (Ornithodoros moubata) Inhabiting Warthog Burrows in ZambiaJournal of General Virology, 1988