Diseases of Indigenous Chickens in Bokaa Village, Kgatleng District, Botswana

a INTRODUCTION According to some authors, African poultry stems from ancient traditional practices 6. Indigenous chickens, otherwise known as traditional or backyard chickens, are local breeds of chickens (Gallus gallus domesticus) reared in rural areas of most parts of the world 19. In these areas they are kept mostly for meat, a source of protein 6. Usually there is very little nutritional supplementation and no proper housing is provided for the chickens. They range freely, scavenging for food and water 20. While in some African countries flock sizes of 20 chickens are not uncommon, in Botswana average flock size has not been established 2. Although indigenous chickens are generally of low body weight, they can be a valuable source of tasty meat and eggs. There is scanty information on the health status and productivity of indigenous chickens. In Botswana, few are vaccinated against common poultry diseases 3. The main objectives of this study were to determine flock size and management, levels of internal and external parasites burdens and seroprevalence of antibod-ies to poultry pathogens in indigenous chickens in Bokaa village, Kgatleng district , Botswana.


INTRODUCTION
According to some authors, African poultry stems from ancient traditional practices 6 .Indigenous chickens, otherwise known as traditional or backyard chickens, are local breeds of chickens (Gallus gallus domesticus) reared in rural areas of most parts of the world 19 .In these areas they are kept mostly for meat, a source of protein 6 .Usually there is very little nutritional supplementation and no proper housing is provided for the chickens.They range freely, scavenging for food and water 20 .While in some African countries flock sizes of 20 chickens are not uncommon, in Botswana average flock size has not been established 2 .
Although indigenous chickens are generally of low body weight, they can be a valuable source of tasty meat and eggs.There is scanty information on the health status and productivity of indigenous chickens.In Botswana, few are vaccinated against common poultry diseases 3 .
The main objectives of this study were to determine flock size and management, levels of internal and external parasites burdens and seroprevalence of antibodies to poultry pathogens in indigenous chickens in Bokaa village, Kgatleng district, Botswana.

MATERIALS AND METHODS
The study was undertaken from August 2003 to February 2004 in Bokaa village in the Kgatleng district, Botswana.Bokaa is located 20 km north of Gaborone.Fourteen randomly selected households were used in the study.A questionnaire was presented to the farmers after they were briefed about its objectives.The questionnaire sought information about the management of the chickens, supplementary feeding, reasons for rearing chickens, water supply, treatment, vaccinations, flock size, causes of mortalities, supplementary sources of income, and gender of the poultry keeper.
During farm visits, hens and cocks were counted, weighed and inspected for signs of anaemia and the presence of ectoparasites.Chicks were those birds which were 3-4 months old and accompanied by a hen.The chickens were gently restrained to expose the brachial vein, the preferred site for venipuncture in birds.The site was cleaned with 'Savlon' followed by 70 % ethanol.Blood was collected into sterile vacutainer tubes without anticoagulant and the serum thus separated was stored at -20°C in 1 m aliquots.
Ten adult indigenous chickens were bought from 10 different households in Bokaa during the wet summer months, January to February 2004.The birds were starved for a day before post mortem examination was performed.The respiratory and digestive tracts were systematically examined after being separated into trachea, oesophagus, crop, proventriculus, gizzard, and small and large intestines.
The contents of each part of the visceral organs were emptied into separate Petri dishes and the mucosa washed thoroughly with water and later scraped clean with the blunt edge of a scalpel blade.The gut and tracheal washings were examined under a microscope for helmiths.The visible parasites were collected and preserved in 5 % formalin, and later identified and counted 21 .
Serum samples were tested for antibodies to the following poultry pathogens: Mycoplasma gallisepticum, M. synoviae, Newcastle disease (ND), infectious bronchitis (IB) and infectious bursal disease (IBD).Commercially available ELISA kits (Flock check; IDEXX, Westbrook, Maine) were used.The assays were carried out in duplicate serum samples according to the manufacturer 's instructions.
The sample:positive ratios (S/P) were calculated as follows: The cut-off points for the different pathogens were as follows >0.2 for ND, IB, IBD; >0.5 for M. gallisepticum and M. synoviae.Any sera with an S/P ratio above the cut-off point was considered positive.Those below were negative.
Graph Pad Prism statistical software was used to generate means and standard deviations.

RESULTS
In total, 317 chickens were found in 14 households, giving a mean flock size of 22.6 ± 6.85 with a range of 11-34 chickens per household.The mean number of hens and cocks was 8.5 ± 2.4 and 3.0 ± 1.41, respectively.There were 137 chicks, 131 hens and 49 cocks.The ratio of chicks to hens was 1:1.05.The mean body weights of cocks and hens were 2.28 ± 0.56 kg and 1.70 ± 0.38 kg, respectively.
The results of the questionnaire indicated that all the farmers rearing poultry in Bokaa village were females.Fifty per cent of the chickens were kept for domestic consumption and 50 % were for both sale and consumption (Table 1).The egglaying pattern of the chickens could not be established.The chickens brooded the eggs either in the kitchen or in some crude shelter.
Only 14.3 % of the chickens were provided with housing, while the rest (85.7 %) had no shelters.Most chickens (71.4 %) were scavengers.Occasionally they were given food scraps.Commercial feed preparations were given to only 28.6 % of the chickens (Table 1).
Deaths among chickens, caused by disease and predation, accounted for 78.6 % and 21.4 % respectively.Prior to death, the chickens showed signs of diarrhoea, respiratory distress and nervousness.External parasites such as lice, mites and ticks were not seen on physical examination of the birds.
Water was given to the chicks ad libitum.It was also learnt that 7 % of the farmers sought therapeutic intervention at the Animal Health Department, 14 % purchased drugs to treat the chickens and 79 % used traditional decoctions such as Aloe marlothii.None of the farmers ever vaccinated their chickens against common poultry diseases such as ND.
Faecal analysis and post mortem examination of apparently healthy indigenous chickens indicated the presence of 3 helminth parasites, namely Syngamus trachea, Ascaridia galli and Heterakis gallinarum. A. galli was found in the small intestine, and H. gallinarum in the caecum.Syngamus trachea was only recovered from the trachea.Only 1 species of the Cestode genus Raillietina was found in the large intestine and caecum.No helminth parasites were recovered from the oesophagus or crop.

DISCUSSION
The mean flock size of indigenous chickens in the present study was higher than that reported for rural South Africa 5 .It was lower than that recorded in Chitungwiza, Harare, Zimbabwe 10 .It was, however, comparable with that reported for Oodi village, Kgatleng district 15 .The results of the questionnaire reflect the persistent pastoral attitude towards chickens.The study in Bokaa also indicated a gender bias, in that all backyard chickens were reared by women.At least 50 % of the chickens were sold while the rest were kept for domestic consumption.Of interest is that chicken markets are a rarity in Botswana.Eggs from the chickens are traditionally reserved for children and it is taboo for women to eat eggs.Chicken eggs are traditionally reserved for young males for fear of precocious puberty if given to young girls.The questionnaire also showed that chickens were not vaccinated against ND, M. gallisepticum, M. synoviae, IBD or IB.
Most households cited a disease with clinical signs of diarrhoea, dyspnoea and nervous signs as the most common cause of mortality among chickens.It can only be speculated that mortality may have been caused by ND based on clinical symptomatology.This, however, did not exclude the possibility of infection due to IBD, IB and mycoplasmosis, characterised by respiratory distress 9 .These findings corroborate those from Zimbabwe 10 .
In this study, serum from adult indigenous chickens had demonstrable antibodies to ND, IBD and IB.The seroprevalence of IBD in Bokaa was 65.22 %, much lower than that reported for Zimbabwe 10 , but higher than that reported for Oodi. 13Antibodies to IBD have previously been demonstrated in the serum of unvaccinated chickens on farms around Gaborone 11 .In Botswana, IBD has been shown to be endemic and to predispose chickens to other pathogens such as Mycoplasma spp.and ND virus 3 .Other reports on the presence of agglutinating antibodies to M. gallisepticum and M. gallinarum in the sera of indigenous chickens have been cited 12 .It is therefore possible that the high mortalities in chickens reportedly caused by ND could have been exacerbated by mycoplasmosis subsequent to intercurrent IBD.The presence of antibodies to ND among unvaccinated indigenous chickens has previously been established 15 .Since these chickens were over 6 months of age, when maternal antibodies have waned, they could only have been acquired from a natural infection.
Workers in other African countries have also found antibodies to IBD virus 16,18 .There is strong supporting evidence for the susceptibility of indigenous chickens to the virus 11 .While the seroprevalence of M. synoviae and IB were 40.99 % and 34.8 %, respectively, these figures were lower than those obtained for Oodi village, Botswana 13 , and Benin 4 .They were comparable to those reported for Chitungwiza, Zimbabwe 10 .Antibodies to IB virus have been demonstrated in the sera of local chickens in Sudan, although no clinical disease has been reported from Sudan 1 .
The other health constraint encountered was internal parasitism.The nematode parasite A. galli, known to cause heavy infestation in wet and warm environments, was one of the most commonly found parasites in this study, although Botswana is a relatively dry country 21 .Heavy infection with A. galli, resulting in partial occlusion of the intestinal lumen, has been reported in local chickens in Uganda 22 .In contrast to these 2 reports, low infection rates were reported for indigenous chickens in Zimbabwe 8,10 .
Free-ranging predisposes fowls to The rates were lower than those reported for Nigerian chickens 17 and also in southern Ethiopia 24 .Syngamus trachea, known to thrive in humid environments, was found in low numbers in the trachea of some chickens for the first time in Botswana compared with H. gallinarum 10 .Previous reports from other villages did not mention recovery of the parasite from the trachea 14 .It is possible that the low numbers could have been due to the fact that sampling was carried out during a dry period.High temperatures could have destroyed the eggs and infective larval stages.
That poultry farmers resort to traditional decoctions of dubious efficacy to treat sick chickens has also been alluded to in the literature 7 .Indigenous poultry farmers resort to traditional decoctions because they are readily available.There is a need to establish the efficacy of these widely used decoctions.
Apart from the poor aesthetic appearance of the ascarid worms in the gut, they can cause fatal impaction.Since chickens in this study were heavily parasitised, anthelmintics active against ascarid worms should be administered as has been suggested by some authors 23 .It is also therefore imperative that chickens be given anti-cestodal treatment to prevent unthriftiness among chickens due to malabsorption and possible digestive disturbances.
It is possible to increase production of backyard chickens and commercialise the system.In spite of its acknowledged importance, backyard chicken production is still being hampered by ND outbreaks in some parts of the world.In order to sustain poultry farming and maximise production, vaccination programmes against ND should be introduced.Campaigns to raise the awareness of the indigenous farmers of the importance of ND should be carried out and, if possible, financial support to pay for vaccines should be provided.Annual vaccination against ND and IBD would go a long way towards reducing the incidence of these major diseases of indigenous chickens.