African swine fever : A New Emerging Disease of Pigs
Dr Parvinder Kaur Lubana , Deputy Director A.H. ,NRDDL Jalandhar Punjab.
Abstract :-
African Swine Fever (ASF) is a highly infectious and contagious hemorrhagic viral disease of pigs, wild boar/feral pigs. Pig species of all breeds and ages. Transmitted through direct and indirect contacts, ingestion of contaminated feedstuffs and by certain tick vector species. ASFV is a DNA virus of the Asfarviridae family and genus Asfivirus. Mortality rate is as high as 100% The disease does not infect humans (not Zoonotic) or other livestock species. The incubation period varies from 4 to 19 days.However, no vaccine or drugs are available to prevent ASF infection at present.
ASF was detected first in 1921 in Kenya and is generally prevalent and endemic in countries of sub-Saharan Africa, Europe and in some Caribbean countries. India notified the first outbreak of ASF virus in January, 2020 in the North Eastern States of Assam and Arunachal Pradesh.
Symptoms The clinical syndromes vary from per-acute, acute, sub-acute to chronic form depending on various factors like virus virulence, swine breed affected, route of exposure, infectious dose, and endemic status in the area.
Per-Acute form – High fever (41-42 °C) and sudden death within 1-3 days.
Acute form – High fever (40-42°C) with reddening of skin of ear tip, tail, ventral
aspects of chest and abdomen, and death within 6-9 days for highly virulent strains, or 11-15 days for moderately virulent isolates. Mortality upto 90-100 % .
Reddening of skin of ear tip
Sub-acute form – Slight fever, reddening of skin and death within 15-45 days. Mortality between 30-70% .
Reddening of skin
Chronic form – The mortality rate in this form is less than 30%. Pig shows irregular peaks of temperature, respiratory signs, necrosis in skin, ulcer, arthritis, joint swelling.
Lactating piglets
- Vomiting & Diarrhea
- High Fever &Conjunctivitis.
- Sudden death.
- Very weak piglets at birth (congenital tremor).
- High mortality.
Sows
- Loss of appetite and high fever
- Abortions.
- Increment of stillbirths.
- Increment of mummified piglets.
- Seizures.
- Diarrhea.
- General reproductive failure.
- Blue discoloration of the skin.
Nursery and fattening animals
- Depressed pigs – with their head down.
- Diarrhea and anorexia
- Eye discharge and persistent fever
- Seizures and Lack of coordination.
- Blue discoloration of the skin.
- High mortality.
Transmission
The virus can spread through blood, tissues, secretions and excretions of sick and dead animals. Recovered pigs may also act as carrier. There are various modes of transmission,
Direct Transmission: – Contact between sick and healthy animals .
Indirect Transmission:– Feeding of garbage( swill) containing ASF infected meat
(ASFV can remain infectious for 3–6 months in uncooked pork products) .
Fomites include premises, vehicles, equipment, clothes.
Biological vector:– Soft ticks of genus Ornithodoros .
Post-mortem (PM) Lesions
Diagnosis is the first step in the process of controlling or containing a disease. Accordingly, it is necessary for Veterinarians to observe PM lesions to support clinical diagnosis of the disease.
Acute form – Haemorrhage in renal and gastro-hepatic lymph nodes, congestive splenomegaly, cutaneous ecchymoses on legs and abdomen, petechiae in mucus membranes of larynx, bladder and visceral surfaces, edema in mesenteric structures . There may also be excess haemorrhagic fluid in the body cavities and gelatinous fluid in the lungs
Chronic form – Focal caseous necrosis and mineralization of lungs, enlarged lymph node Acute forms can be confused with Classical Swine Fever (CSF) and other diseases like Swine Erysipelas, Poisoning, Salmonella, Pasteurellosis, Pseudorabies and other septicaemic conditions. Therefore, laboratory confirmation is important and a must for confirmatory diagnosis
Hemorrhages on kidney and heart Enlarged spleen Hemorrhages S.I.
Samples for lab.
In live animals :– Blood in EDTA 2ml
Serum 2ml
In dead animals :– Spleen , Tonsils and lymph nodes
No preservative should be added in tissue samples .and send on ice as early as possible .
Performa for sample submission
| Sr.no | Name of owner and address | Total animals affected /mortality | Age and sex of animal | Clinical signs | Sample type | Sample code |
Laboratory diagnosis: The laboratory diagnosis consists of:
Virus isolation
Detection of genomic DNA by Real-time PCR.
Treatment :– There is no treatment and vaccination . All infected animals must be isolated and culled immediately upon confirmation of presence of the virus.
Control :–
It divides the pig population of the Country in 3 different subpopulations
Infected zone (IZ) – 1 Km radius of infected premises (IP)
Intermediate / Surveillance zone (SZ) – 10 Km radius from the infected premises (9 km outside the IZ)
Disease Free zone /Non-Infected area (FZ) – Area outside the SZ
Bio-security
Bio-security measures
- Disinfection of area, personal hygiene of animal owners and handlers
- Farms should be kept under strict hygienic and bio-secured condition at all times including proper fencing to prevent disease transmission from domestic pigs to wild pigs and vice-versa.
- Additionally, scavenging-based pig production system should be avoided.
- Ensure there is no dumping of waste material from pig meat shops and pig farms. All waste material should be destroyed / disposed of preferably.
- Stop swill feeding practices, both from the domestic kitchens and from restaurant kitchen, considered to be one of the major risks for the spread of the virus.
- Prevent pigs from wandering to avoid contact with soft ticks vectors.
- Enhance awareness among all pig farmers and other stakeholders.
Control measures in a Feral Pig :– (FPCZ)
Prevention of contact between feral and kept pigs.
All kept pigs on the premises should be restricted to their living quarters
Feral pigs should be prevented from gaining access to any material that might come into contact with the pigs on the premises.
Restriction of pig movements – Pigs should not be moved on to or out of the premises.
Appropriate means of disinfection should be provided and used at the entrances and exits of those parts of the premises in which pigs are being kept and of the holding itself.
No carcass or any part of a feral pig should be brought onto a premises in the FPCZ
Carcasses of any feral pigs shot by owners on their premises to protect stock must be isolated from kept pigs and made available for examination, sampling and testing.
Keepers should instigate cleansing and disinfection of the location the feral pig was shot, where appropriate, to reduce the potential of virus spread
Other measures • No pig, semen, ovum or embryo should be moved out of the control zone except under license.
Any person who comes into contact with a feral pig in the infected area should take steps to ensure they do not spread infectious or potentially infectious material
Any person who finds the carcass of a feral pig should immediately inform officials so that the carcass can be sampled and tested for African swine fever.
Lifting of FPCZ :-The FPCZ will be lifted after disease eradication is completed. However, the monitoring will continue in the area for at least 24 months after the last case of African Swine Fever in feral pigs, in order to support the cause for regaining disease freedom.
Feral = wild, swill = feeding garbage , Splenomegaly= enlarge spleen
Mummified piglets = large and dead piglet
Infected zone = area of infection
REFRENCE = field experience and national action plan of control of ASF
Pictures are taken from net
