African Swine Fever
Dr Menalsh Laishram
African swine fever (ASF) is a highly infectious deadly disease of pigs-domestic and wild alike, affecting all ages. Just by the name the disease can be confused with the Classical Swine fever prevalent in the region from before but, the symptoms are far more severe in nature than the later.
Distribution of the disease: Recently the distribution of the ASF expands across in more than 50 countries in three continents namely- Africa, Asia and Europe. Numerous outbreaks of ASF out of Africa were reported between 1960s and 1970s. The disease was first detected in Georgia, in 2007 from where it spread to neighbouring countries comprising the Russian Federation. From there ASF spread to EU in 2014. In August 2018, China reported the first outbreak of ASF and till date the spread of the disease has not been stopped.
Causative organism: ASF is caused by a DNA virus known as Asfivirus of the family Asfarviridae. ASF virus is biologically spread by wild pigs which may remain as reservoir of infection and by soft ticks of the Ornithodoros genus especially O. moubata and O. erraticus. Transmission is also caused by infected meat and by contact though fomites (indirect contact by infected pens and contaminated feeds). The body secretions and discharges like feces vomitus are also a source for infection.
Signs and symptoms: The incubation period of the ASF is usually 4-19 days. It is a highly contagious disease and may have chronic and per-acute stages which act as a carrier of the virus. The acute form is manifested by high fever, loss of appetite, incoordination of gait and difficulty in walking, bluish bloody patches in the skin mostly on the ear, extremities of limb, perineal and inguinal region, ventral surfaces of the abdomen, thorax and axilla and internal organs, death in 4-10 days, sometimes even before the first clinical signs are observed. Case fatality rates may be as high as 100%. The disease is not a threat to humans, but humans can act as a mechanical vector in the spread of the disease due to the contaminated feeds and equipment. And pigs are the only domestic animals which are affected by the ASF.
Treatment: There is no vaccine available for the disease, and the pigs which are given vaccines of classical swine fever (CSF) are also susceptible. Satisfactory treatment is not available against this disease so far.
Control: All movements of pigs are to be prohibited. Contact of vectors, animal attendants, veterinarians with the diseased pigs should be avoided. The healthy pigs are to be attended first and the sick and the suspected pigs later. Strict quarantine, isolation and culling must be adopted to prevent further spreading of the disease. Culling of the pig immediately upon confirmation of the disease is advised. Dead animals must be burnt or buried and the whole farm premises should be properly disinfected.
The farm premises are to be cleaned regularly by white washing and the floors with bleaching powder or, 1% caustic soda (NaOH). Equipment and utensils are to be disinfected with 37% formaldehyde or formalin. Foot baths are to be filled with potassium permanganate solution (3: 10000) or, 1% lime at entrance of the farm premises. Proper and strict of biosecurity measures are to be adopted.
Scenario in Manipur: The local market in Manipur for instance is under threat due to the illegal poaching and import of pigs across the borders with Myanmar and the state of Assam which have already confirmed cases of ASF. The ban of import and export of pigs has been ordered by the government of Manipur which is crucial for stopping the disease. But for the time being there has been no reports or suspected cases so far. We need to prepare for the worst, and the farmers need to be vigilant and regular inspection is necessary, reporting immediately to a Veterinarian or the concerned authorities if any suspected cases arise.
About the author : PhD Scholar, WBUAFS, Kolkata