Livestock production is an important feature of the country's agriculture, contributing considerably towards meeting food needs and generating cash income. The livestock subsector contributes only 9 percent of the total agricultural GDP. The level of domestic production is only 23 percent of the national demand of 195 000 tonnes. The per caput consumption of 5 g/head/day is among the lowest in sub-Saharan Africa and is far below the recommendations of both FAO and the World Health Organization (WHO). The government decided to use both pigs and poultry on account of their high prolificacy in its accelerated plan of solving the meat deficit in the short term. Apart from the high cost of feeding pigs, the pig industry is now plagued with a devastating viral disease, African swine fever (ASF).
The disease was first reported in West Africa in Senegal in 1978 and retrospective studies carried out indicated that ASF was present in Casamance and Guinea Bissau. Other outbreaks were reported in Cameroon in the mid- and late 1980s. Although not reflected in OIE bulletins, ASF was confirmed for the first time in Cape Verde in 1980. In 1996, Côte d'Ivoire was stricken by an ASF epidemic, while in 1997 Benin, Togo and Nigeria joined the ranks of the affected countries. Pig losses have been very heavy, resulting in some countries losing one third or more of their pig population.
When these outbreaks were reported, Ghana took stringent measures to prevent the entry of the disease into the country. With a growing pig population of approximately 355 000 (1996 livestock census), Ghana was unfortunately stricken with ASF in September 1999, in spite of four years of strenuous effort by the Ministry of Food and Agriculture to prevent the disease. As of September 2000 the disease has been reported in the following districts:
An active disease surveillance programme instituted with the help of the Epidemiology Unit included techniques such as a participatory epidemiology and questionnaire survey. The field staff also embarked on clinical surveillance. The initial participatory epidemiology was effected with the assistance of FAO consultant, Dr Glyn Davies, while the questionnaire survey was initiated by Dr Mary-Lou Pernrith.
From the participatory epidemiology, it was deduced that the disease outbreak occurred in September 1999 and the first detected focus was at a cluster of pig farms at Awoshie, a suburb of Accra. The spread from Awoshie to Bawjiase, a town in the contiguous district in Central region, was through movement of pigs assumed to be healthy from the outbreak areas to a "safe" area. The map below shows the various outbreak foci in the country.
There was also a possibility of association of ethnicity to the spread of the disease in some areas. Most of the pig farmers and women who trade in pork in the outbreak areas Awoshie, Tema and Ashiaman are of Ada origin. Movement of apparently healthy pigs to their relatives at home could be an explanation for the spread of the disease to Dangme East (Ada) district. At Ocanseykope, two women traders in vegetables (tomatoes) were said to have smuggled infected pork from Awoshie and Ashiaman (previous outbreak areas) to sell at Togbloku and Ocanseykope in Dangme East (Ada) district.
In a survey questionnaire, 5 000 copies of an epidemiological inquiry for ASF have been answered by pig farmers throughout the country using veterinary field staff as interviewers. Data input is not yet complete but a preliminary analysis of 2 500 completed questionnaires identifies the following variables as risk factors:
Type of rearing system
Three rearing systems have been identified: permanent housing; not always confined; never confined. The permanent confinement of pigs has a limiting effect on the spread of ASF. During the ASF surveillance at Kpone in the Tema Metropolitan Assembly, the importance of permanent confinement of pigs became evident. None of the farms with double walling was affected. All of the pigs reared in the "never confined" and "not always confined" systems were affected.
Attitude towards breed type
Breed types were classified as exotic, crossbred and local. The farmers' perception that the local breed can fend for itself was apparent: during the ASF outbreak, this category of pigs registered the highest mortality.
Feed and feed source
In the epidemiological inquiry, most of the respondents mentioned the following as the types of feed given to their pigs: agricultural by-products, swill, greens and fish remnants. Swill, in this sense, means leftover food from homes, restaurants, "chopbars", school dining halls, ships and aircraft. It appears that the introduction of ASF in Ghana was associated with swill dumped from a ship at the Tema main refuse dump. Two farmers near the refuse dump allowed their pigs to scavenge at the dump, resulting in the outbreak on their farms.
Source of replacement stock
Replacement stock is categorized as being acquired through the following sources: own breeding; purchased from livestock markets; from neighbours, friends, family members who own pigs; commercial breeders. It was realized that in Ashiaman a farmer brought in apparently healthy pigs from Kpone before the outbreak started in the area.
Marketing of pig and pork products
After the disease was introduced, the marketing of pigs seems to be the main source of spread of the disease within the country. A probable source of the outbreak was through the importation of pig products from Togo. Our surveillance revealed that during the outbreak of ASF in Togo some supermarkets were importing pork and other pig products through and from Togo.
Disposal of ASF carcasses
The main methods of carcass disposal identified were by burial, disposal on a garbage dump, consumption and, sometimes, sale to the public. Where people dispose of carcasses by throwing them on to a garbage or refuse dump, scavenging pigs can easily become infected by feeding at the refuse place.
Use of animal health services
Most areas where the outbreak occurred were staffed by a trained Agricultural Extension Agent with a crop bias.
A team composed of an epidemiologist and two field officers paid a working visit to pig farms in Akwapim South and North districts to identify farms with a sound management practice and having good weaners in stock which can be purchased for sentinel purposes in order to restock ASF-affected farms.
Laboratory reports on these farms from Onderspoort Veterinary Institute Laboratory in South Africa indicated the absence of ASF exposure.
The virus is known to survive in such adverse conditions as extreme cold and moderate temperatures. At 4oC (the normal temperature for food preservation) it can survive for seven years, but would live even longer in a deep-freeze. The implication of this characteristic of the virus is that farmers who must have hidden slaughtered pigs in deep-freezes waiting to sell them when the ban on movement of pig and pork products is lifted are a potential threat.
The illegal Importation of pig meat and other pork products through and from Togo into the country poses a threat.
The number of scavenging (free-roaming) pigs to a large extent encouraged the spread of the disease. However, in Ghana, there are by-laws restricting the free-roaming of pigs which are never adhered to. Failure to enforce these by-laws can cause a return of the disease.
(Contributed by: George Nipah, Epidemiology Unit, Veterinary Services Department, Accra, Ghana.)