Molecular Characterization of Foot-and-Mouth Disease Viruses Collected in Tanzania Between 1967 and 2009.

This paper describes the molecular characterization of foot-and-mouth disease viruses (FMDV) recovered from outbreaks in Tanzania that occurred between 1967 and 2009. A total of 44 FMDV isolates, containing representatives of serotypes O, A, SAT 1 and SAT 2 from 13 regions of Tanzania, were selected from the FAO World Reference Laboratory for FMD (WRLFMD) virus collection. VP1 nucleotide sequences were determined for RT-PCR amplicons, and phylogenetic reconstructions were determined by maximum likelihood and neighbour-joining methods. These analyses showed that Tanzanian type O viruses fell into the EAST AFRICA 2 (EA-2) topotype, type A viruses fell into the AFRICA topotype (genotype I), type SAT 1 viruses into topotype I and type SAT 2 viruses into topotype IV. Taken together, these findings reveal that serotypes O, A, SAT 1 and SAT 2 that caused FMD outbreaks in Tanzania were genetically related to lineages and topotypes occurring in the East African region. The close genetic relationship of viruses in Tanzania to those from other countries suggests that animal movements can contribute to virus dispersal in sub-Saharan Africa. This is the first molecular description of viruses circulating in Tanzania and highlights the need for further sampling of representative viruses from the region so as to elucidate the complex epidemiology of FMD in Tanzania and sub-Saharan Africa.

Genetic characterization of African swine fever viruses from a 2008 outbreak in Tanzania.

Outbreaks of African swine fever (ASF) have been reported in the past from several countries in sub-Saharan Africa. The aim of this study was to genotype ASF viruses (ASFVs) from the 2008 outbreak in Morogoro and Dar es Salaam regions of Tanzania. Tissue samples from domestic pigs that died as a result of severe haemorrhagic disease were collected and analysed with PCR and genome sequencing methods using ASFV-specific primer sets. Nucleotide sequence data were obtained for the B646L (p72), E183L (p54) and the variable region of the B602L gene sequences. Phylogenetic analyses based on DNA sequences showed that the 2008 Tanzanian isolates belonged to p72 genotype XV and clustered together with those derived from the 2001 outbreak in Tanzania. Analysis of the tetrameric amino acid repeat regions within the variable region of the B602L gene showed that the repeat signature of the 2008 Tanzanian ASFV was unique and contained three novel tetramers (U = NIDT/NTDT and X = NTDI). Epidemiological investigation suggested that transportation of live pigs continues to play an active role in the epidemiology of ASF in Tanzania. It is recommended that future control of ASF spread in Tanzania should focus on the early detection and confirmation of the disease, prompt institution of quarantine measures, culling and proper disposal of infected and in-contact animals and decontamination of affected premises.

Phenotypes including immunocompetence in scavenging local chicken ecotypes in Tanzania.

A study was conducted to determine the variations in physical characters and immunocompetence among scavenging local chicken ecotypes in Tanzania. Eighty-four adult scavenging local chickens from four eco-climatic regions of Tanzania were studied. Measurements of adult body weight, body length, shank length and egg weight and observations of plumage colour and pattern, earlobe colour, skin colour and the shape of the comb were conducted. The antibody response to sheep red blood cells, serum haemolytic complement and the cutaneous response to phytohaemagglutinin-P were assessed. Five ecotypes were identified and named Mbeya, Morogoro-medium, Ching'wekwe, Kuchi and Singamagazi. Singamagazi and Kuchi were significantly heavier, with longer shanks and heavier eggs than the other ecotypes. The average adult body weight for males ranged from 1621 g (Mbeya) to 2915 g (Singamagazi). Average female weights ranged from 1108 g (Morogoro-medium) to 2020 g (Singamagazi). Mean egg weights ranged from 37.65 g (Ching'wekwe) to 45.61 (Singamagazi). The Kuchi had mostly rose and walnut combs, while the other ecotypes were mostly single combed. In each ecotype there were chickens with a high or low antibody response to red blood cells, but there was a significant difference between the ecotypes.

Molecular epidemiology of Salmonella gallinarum in chickens in Tanzania.

A molecular epidemiological investigation of Salmonella gallinarum infection in scavenging local chickens and commercial layers in Tanzania was conducted between August 1997 and April 1998. A total of 1152 chickens were randomly selected from 10 villages and seven commercial farms. For serological and cultural prevalence studies, 1152 blood samples and 912 cloacal swabs were collected. In scavenging local chickens, the individual serological and cultural prevalences were 6.3 and 0%, while the prevalences were significantly higher in commercial layers at 18.4 and 2.6% (P < 0.001), respectively. The risk of infection in flocks of scavenging local chickens that had contact with commercial chickens was six times greater than the risk of infection in flocks of scavenging local chickens that had no contact with commercial chickens. Thirty-four S. gallinarum isolated from commercial chickens in this study, together with 29 Tanzanian historical isolates, were characterized using plasmid profiling and ribotyping. Fifty-one isolates contained both 85 and 2.5kb plasmids, five isolates contained only one plasmid of 85kb, and seven isolates had no plasmids. Ribotyping using HindIII restriction endonuclease demonstrated seven different ribotypes. Forty-seven isolates had similar results in both typing systems, suggesting they belonged to one clone. It is concluded that S. gallinarum infection in chickens in Tanzania is more prevalent in commercial layers than in scavenging local chickens. One strain of S. gallinarum from chickens first isolated in a Dar es Salaam hatchery was found to be common throughout the country.

Evaluation of the efficacy of the crude extracts of Capsicum frutescens, Citrus limon and Opuntia vulgaris against Newcastle disease in domestic fowl in Tanzania.

Prophylactic and therapeutic efficacy of a combination of Capsicum frutescens (red pepper), Citrus limon (lemon) and Opuntia vulgaris (prickly pear) against Newcastle disease (ND) in domestic fowl were evaluated. Eighty-eight broiler chickens were divided into five groups. Birds from three groups were inoculated with velogenic ND virus strain, whereas birds from two groups were left as controls. Two groups received a mixture of the plant extract three days prior to inoculation and birds from one group were given the plant extract for two days following development of clinical signs. Blood samples were collected for haemaglutination inhibition tests (HI) for detection of ND virus antibodies. Body weights were monitored during the experiment. Three birds died from the group that was inoculated with ND virus and treated with the plant extract; two died from the group that received the plant extract as a prophylaxis and inoculated with ND virus; and one bird died from the group that was inoculated with ND virus but not given the plant extract. No death was observed in any of the birds in the control groups. Antibody titers for ND virus rose four-fold in the inoculated birds but remained low in the un-inoculated groups. Mean body weights of birds in group B declined markedly compared to the other groups. The results indicated that there was no prophylactic or therapeutic value of the plant extract against ND. The plant extract showed a negative effect on body weights in birds with ND.