African Swine Fever
Lalrinkima1*, R. Ralte2, S. Azmi1
1Department of Veterinary Pathology, Khalsa College of Veterinary and Animal Sciences
2Department of Veterinary Microbiology, Khalsa College of Veterinary and Animal Sciences
Introduction
African swine fever (ASF) is a viral disease of swine leading to high mortality in domestic pigs and wild pigs reaching almost 100% mortality. The diseases has been listed into the category as “notifiable disease” by the World Organization for Animal Health (OIE). It causes important economic losses that are unavoidable in the absence of an effective vaccine and the available methods of disease control are the quarantine of the affected area and culling of the infected animals. The disease caused by this virus was first identified in Kenya in 1920.
India report the first outbreaks of African swine fever virus in Assam and Arunachal Pradesh states on February 2020. By June 2021, the disease has spread to other parts of Northeastern states such as Meghalaya, Mizoram, Manipur and Nagaland which leads to high mortality among the pigs farmers.
Etiology
ASF is caused by ASF virus (ASFV) a double-stranded DNA virus with a complex molecular structure. It is the only member of the Asfarviridae family and the only DNA virus transmitted by arthropods soft ticks of the Ornithodoros genus.
Transmission
African swine fever can be spread through direct contact with infected pigs, feces or body fluids and indirect contact via fomites such as equipment, vehicles or people who work with pigs between pig farms with ineffective biosecurity. Pigs eating infected pig meat or meat products is also one of the most important source of transmission. The diseases is transmitted by arthropods soft ticks of the Ornithodoros.
Clinical signs
Clinical signs of the disease are most likely to be per acute or acute form. Even with lower viral titer, infected pigs start showing symptoms from two to three days after infection, but can also take 15 days to develop with very low virus doses. Increase in body temperature (>41°C), loss of appetite, dullness, huddling together, reluctance to move, red-purple skin discoloration especially in the extremities (e.g. ears) and ventral body surfaces, visible hemorrhages are sometimes manifested, but pigs may die without showing external lesions. Clinical signs that are more variable and may not be present in all pigs or in all groups of pigs include gastrointestinal signs such as vomition and diarrhoea/dysentery. Nervous signs such as ataxia and other signs – oculonasal discharges, epistaxis, dyspnea and coughing are also manifested.
Postmortem lesions
On postmortem examination, the pericardial and thoracic cavities were filled with straw tinged fluid, petechial hemorrhages was seen on the heart especially at the atrioventricular junctions. There was presence of hemorrhages on the gastrohepatic lymph node. Intestine and mesenteric lymph nodes showed severe haemorrhages.
Haemorrhages in the heart Haemorrhages in the intestine
Diagnosis
Based on the history, clinical signs and symptoms. ASFV genome detection by polymerase chain reaction (PCR). Antigen detection by direct fluorescent antibody test (FAT) and isolation of the virus. Detection of the antibodies by ELISA, Indirect fluroscent antibodies, indirect immunoperoxidase test.
Differential diagnosis
Differential diagnosis of African swine fever virus includes classical swine fever (CSF), Porcine reproductive and respiratory syndrome (PRRS), Porcine dermatitis and nephropathy syndrome (PDNS), swine Erysipelas, Aujeszky’s disease, Salmonellosis (and other bacterial septicaemias) and Poisoning.
References
- Abedin, S. N., Baruah, A., Bora, A., Dutta, D. and Dutta, A. J. P. I. (2020). African swine fever (ASF) outbreak in India: A review of literature about the virus and its control measures. Pharm Innov, 9(7), 298-304.
- Food and Agricultural organization (FAO). African swine fever detection and diagnosis.
- Galindo, I. and Alonso, C. (2017). African swine fever virus: a review. Viruses, 9(5), 103.
- https://www.fda.gov/animal-veterinary/safety-health/african-swine-fever
- https://www.pashudhanpraharee.com/african-swine-fever-asf/#:~:text=The%20African%20swine%20fever%20(ASF,huge%20economic%20and%20production%20losses.
