S.M. Arimi

Brucellosis in sub-Saharan Africa: epidemiology, control and impact

Brucellosis is an important disease among livestock and people in sub-Saharan Africa. In general, the incidence is the highest in pastoral production systems and decreases as herd size and size of landholding decreases. The prevalence of risk factors for infections are best understood for bovine brucellosis and to a lesser extent for ovine and caprine brucellosis. The occurrence and epidemiology of brucellosis in pigs is poorly understood. This species bias is also reflected in control activities. As with other public-sector animal health services, the surveillance and control of brucellosis in sub-Saharan Africa is rarely implemented outside southern Africa. Brucellosis is even more ignored in humans and most cases go undiagnosed and untreated, leading to considerable suffering for those affected. Decision-making to determine the importance of brucellosis control relative to other public concerns and what brucellosis control strategies should be applied is urgently required. A strategy for how brucellosis decision-making might be considered and applied in future is outlined.

Diversity of Listeria ribotypes recovered from dairy cattle, silage, and dairy processing environments

Listeria strains isolated over the past 10 years from farms and dairy processing environments were subjected to strain-specific ribotyping using the automated Riboprinter microbial characterization system, alpha version (E. I. du Pont de Nemours & Co., Inc.). A total of 388 Listeria isolates from 20 different dairy processing facilities were examined along with 44 silage, 14 raw milk bulk tank, and 29 dairy cattle (26 udder quarter milk, 1 brain, 1 liver, and 1 aborted fetus) isolates. These 475 isolates included 93 L. monocytogenes , 362 L. innocua , 11 L. welshimeri , 6 L. seeligeri , 2 L. grayi , and 1 L. ivanovii strains. Thirty-seven different Listeria ribotypes (RTs) comprising 16 L. monocytogenes (including five known clinical RTs responsible for foodborne listeriosis), 12 L. innocua , 5 L. welshimeri , 2 L. seeligeri , 1 L. ivanovii , and 1 L. grayi were identified. Greatest diversity was seen among isolates from dairy processing facilities with 14 of 16 (87.5%) of the L. monocytogenes RTs (including five clinical RTs) and 19 of 21 (90.5%) of the non- L. monocytogenes RTs detected. Sixty-five of the 93 L. monocytogenes isolates belonged to a group of five clinical RTs. These five clinical RTs included one RT unique to dairy processing environments, two RTs common to dairy processing environments and silage, and one RT common to dairy processing environments, silage, and dairy cattle with the last RT appearing in dairy processing environments, silage, raw milk bulk tanks, and dairy cattle. These findings, which support the link between on-farm sources of Listeria contamination (dairy cattle, raw milk, silage) and subsequent contamination of dairy processing environments, stress the importance of farm-based HACCP programs for controling listeriae.

Occurrence of 'thermophilic' campylobacters in sewage and their removal by treatment processes.

Removal of thermophilic campylobacters from sewage at three different stages of treatment at a trickling filter sewage works has been assessed. Samples of incoming sewage, primary sedimentation effluent and final effluent were taken daily from 06.00 h to 20.00 h for 5 consecutive days and the numbers of campylobacters determined by using a most probable number method. Each sample was cultured using 2 h pre-enrichment followed by enrichment in Preston broth for 48 h and detection by plating. Over 78% of the incoming campylobacters were removed after primary sedimentation and less than 0.1% remained in the final effluent. Campylobacter jejuni biotype I and biotype II constituted 81.5% and 15.9% respectively of the 232 isolates tested. Serotypes common in sewage were common in human faeces. It appears that the trickling filter sewage works removes most of the campylobacters entering the sewage works, but large numbers, estimated to be approximately 10(10), are released into the environment daily from a local sewage works.

A longitudinal study of milk somatic cell counts and bacterial culture from cows on smallholder dairy farms in Kiambu District, Kenya.

As part of an integrated study on health and production of dairy cattle on smallholder farms in central Kenya, quarter-milk samples, survey and production data were collected monthly for one year from 210 lactating cows on 89 farms. Each of these cows was sampled at least once during the study period. Farms were selected in a 2-stage stratified random sample. Average milk yield was low (5.8 kg/day; median = 5 kg/day) and lactation length was long (20 months). Clinical mastitis risks were low (1% per month). Somatic cell counts (SCC) were high (median = 620 × 103); the previously suggested threshold of 300000 cells/ml would classify 71% of quarters as positive for subclinical mastitis. Bacteria were commonly isolated, with S. aureus the most-common pathogen isolated (22.1% of all samples). Infections with mastitis pathogens, cow-age and milk yield were associated with increases in SCC. However, S. aureus was the only mastitis pathogen associated with decreased milk yield. Few specific mastitis-control measures were applied. The only farm-level variable associated with high SCC was the method of drying off. Gradual drying off decreased SCC.

Isolation and characterization of group B streptococci from human and bovine sources within and around Nairobi.

Group B streptococci (GBS) were isolated from bovine milk and from vaginas and throats of antenatal and postnatal women using TKT and rapid GBS media. Sixty-three of 529 (12%) bovine bulk milk samples, 9 of 48 (19%) vaginal and 3 of 48 (6%) throat samples were positive. Both bovine and human beta haemolytic isolates were characterized biochemically and serologically. Pigment production was a characteristic of both human and bovine beta haemolytic isolates. The majority (88%) of human isolates fermented salicin and not lactose and most bovine isolates were either lactose positive/salicin positive (41%) or lactose positive/salicin negative (38%). Human and bovine isolates were 100% and 85% typable respectively. Serotype distribution was similar in the bovine and human populations with serotype la, lc and lll being most common in both. Fermentation of sugars showed major differences between bovine and human isolates but similarity in serotype distribution suggests some genetic relationship.

Impact of mastitis control measures on milk production and mastitis indicators in smallholder dairy farms in Kiambu District, Kenya

Bovine mastitis and mastitis control were investigated on smallholder farms in central Kenya. After an initial observational study, a clinical trial to assess the impact of three different mastitis control strategies – (1) improved udder hygiene, (2) treatment of subclinical cases, and (3) a combination of these – was conducted on 100 randomly selected farms with 332 lactating cows. Before the implementation of control measures, the milk yield was low (mean 6.5 kg/day; median 6 kg/day) and somatic cell counts (SCC) were high, with 80% and 43% of cows having milk with SCC greater than 250×103 cells/ml and 600×103 cells/ml, respectively. Infectious pathogens were also commonly isolated, with 63% of cows being positive for pathogenic bacteria. Neither intervention strategy alone had any effect on mastitis indicators or milk yield. In combination, the measures had some impact, lowering the prevalence of contagious pathogens by 18%, but this was not reflected in a significantly increased milk yield, lowered SCC or reduced incidence of clinical mastitis.

Reproductive performance of sows in rural communities of Busia and Kakamega Districts, Western Kenya

This study provided baseline performance of breeding pigs information on local sow productivity that was previously lacking. The objective was to investigate performance of breeding pigs in rural smallholder communities of Western Kenya. A random sample of 288 smallholder farms in Busia and Kakamega districts was selected pigs. The farms were visited three times in the course of the study period, 2006 to 2008. Data on management and productivity were gathered by means of questionnaires administered to sow owners. The average number of sows owned per farm was 1.3±0.6. Sows were bred for an average of 2.18±1.08 days during one estrus. Sows were 12.1±4.5 months old when they farrowed for the first time. They were bred 1.9±1.6 month after piglets were weaned. Sources of breeding boars