African swine fever (ASF)
This diseases can affect pigs of any age. High mortality rates. The key clinical signs include blue-purple cyanosis of snout, ears, tail and lower legs; high fever; and heavy discharge from eyes and nose. This disease is notifiable – contact your vet and local authorities if you believe this disease is affecting your herd.
Clinical signs
High fever 40-42°C.
Loss of appetite.
Depression.
Lethargic- sometimes refusal to stand or move.
Very unsteady when stood up.
Vomiting and/or diarrhoea with bloody discharge.
White skinned pigs: extremities (nose, ears, tail and lower legs) become cyanotic (blue-purple colour).
Discrete haemorrhages appear in the skin particularly on the ears and flanks.
Group will huddle together and are usually shivering.
Abnormal breathing.
Heavy discharge from eyes and/or nose.
Comatose state and death within a few days.
Some pigs can show conjunctivitis with reddening of the conjunctival mucosa and ocular discharges.
Pregnant sows commonly undergo miscarriage or deliver stillborn piglets that are malformed – piglets can be tested for the virus.
Mortality rate in infected groups of pigs is high and there is no vaccination proven to prevent or cure infection, therefore, it is crucial that control begins on-farm. European, South American and Caribbean countries which have been infected have adopted a slaughter policy to eradicate the virus within the herd. Mild strains of the virus also occur which cause a milder but equally serious disease in domestic pig herds – individuals from these herds must also be slaughtered to prevent pathogenesis.
Diagnosis
Pigs that die early in an outbreak may not have any noticeable lesions but as the disease progresses the lesions then are striking. Bright red haemorrhages in the lymph nodes, kidneys, heart and linings of the body cavities are common findings. There may also be excess haemorrhagic fluid in the body cavities and gelatinous fluid in the lungs. The spleen may be enlarged, darkened and crumble on slight pressure.
The veterinarian will have to send samples to a laboratory which specialises in CSF and ASF diagnosis. The best samples to send are blood, lymph nodes, spleen and, in chronic cases, serum for serology. In the case it is CSF and not ASF, the tonsils might also be sent. The veterinarian should consult the appropriate veterinary authorities on how best to send these.
The tonsils of the pig are very easy to find. Laying the dead pig on its back, cut away the skin and flesh under and between its lower jaw bone and tongue. The pair of tonsils are two large red patches each about the size of the end half of your thumb or perhaps slightly bigger. Their surfaces are covered with small pits or depressions.
Cause
African swine fever is caused by the Asfarviridae family of viruses which are distinct from the viruses associated with Classical swine fever. There are 22 known types of the ASF virus, allowing the epidemiological tracing of outbreaks to the source.
The infection can be introduced to uninfected herds in a number of ways:
the feeding of contaminated feed and contaminated food waste used to supplement feed;
through the bites of soft-bodied ticks, lice and flies;
through inoculation with contaminated syringes and use of contaminated surgical equipment; and
through the introduction of infected pigs to the herd.
Transmission of the virus within the herd is generally through direct contact with infected bodily discharges, faeces and vomit.
Prevention
There is no live or attenuated vaccine for the prevention of ASF therefore control of the virus is reliant on strict biosecurity.
Do not feed domestic pigs food waste; this is illegal in the UK, other EU regions and some states within the US
Where ‘permitted garbage feeding’ is legal in US states, pigs fed this way are prohibited from exportation.
Do not leave food waste exposed for wild swine species to access. Dispose of food waste properly.
Abide by strict biosecurity rules. Do not take pig meat onto farms, or restrict all food (and consumption of food) to a canteen. All staff on farm should be inducted onto a strict programme of hand and equipment sanitisation before and after contact with pigs.
Follow rules and regulations on disposal of food waste at ferry ports and airports.
Provide the means for staff and visitors to thoroughly sanitise their hands and equipment.
Ensure that wild boar, warthogs and wild pigs, and materials potentially contaminated by such wild species do not come into contact with domestic pigs.
Check infected regions before import of goods that could potentially be contaminated.
Advise and educate people on the risks of bringing back pork products from infected regions.
Treatment
There is no treatment.
All infected animals must be isolated and culled immediately upon confirmation of presence of the virus.
By-Dr Parvinder Kaur Lubana
NRDDL,JALANDHAR, PUNJAB
