Diversity of Taenia and Hydatigera (Cestoda: Taeniidae) in domestic dogs in Kenya.

Taenia species of domestic dogs can cause cysticercosis and coenurosis in a wide range of intermediate hosts including humans. Most taeniids of dogs are globally distributed, but some wildlife-transmitted species can be specific for certain regions. Generally, little information exists on the species composition and frequency in most regions of the world, which impairs risk assessment and control strategies. This study determined the range of taeniid species in dogs in four widely spaced areas of Kenya by genetic identification of eggs in faeces collected from the environment. Individual taeniid eggs were characterised by nested polymerase chain reaction of NADH dehydrogenase subunit 1 and cytochrome C oxidase 1 genes, restriction fragment length polymorphism and partial sequencing. Overall 79/1621 (4.9%) faecal samples contained eggs of Taenia or Hydatigera (8.0% in Turkana, 4.8% in Isiolo, 3.8% in Maasai Mara and 1.3% in Meru). Taenia hydatigena and T. multiceps were the most frequent, found in 36 and 15 samples, respectively. Other eggs found in the faeces belonged to T. serialis (sensu lato), T. madoquae (the first record in domestic dogs), T. ovis, T. saginata and Hydatigera taeniaeformis. Polymorphism of nad1 sequences revealed 22 and 8 haplotypes of T. hydatigena and T. multiceps, respectively. The results show the involvement of dogs in both domestic and sylvatic transmission cycles. In addition to the species range, this study provides data on the intraspecific diversity of T. hydatigena and T. multiceps in Kenya, which will serve as baseline information for further studies into cysticercosis and coenurosis in livestock and humans in the region.

Molecular characterization of Echinococcus species in dogs from four regions of Kenya.

Cystic echinococcosis is endemic both in livestock and humans in many parts of Kenya. However, very little data exists on Echinococcus infections in dogs, and therefore their role in maintaining the transmission cycles and environmental contamination with eggs of Echinococcus species is unknown. The study aimed to establish the prevalence and distribution of Echinococcus granulosus sensu lato causing infection in dogs in Kenya. A total of 1621 dog faecal samples were collected from the environment in four different regions and examined microscopically for the presence of taeniid eggs. Up to 20 individual taeniid eggs per faecal sample were picked, lysed and genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequencing of the NADH dehydrogenase subunit 1 (nad1) gene. Eleven percent (178/1621) of faecal samples had taeniid eggs, while 4.4% (71/1621) contained Echinococcus spp. eggs. Area-wise, the faecal prevalence of Echinococcus spp. was 9.2% (48/524) in Turkana, 4.0% (20/500) in Maasai Mara, 0.7% (2/294) in Isiolo and 0.3% (1/303) in Meru. E. granulosus sensu stricto (s. s.) was the dominant Echinococcus taxon, followed by E. canadensis (G6/7) that was detected in 51 and 23 faecal samples, respectively. E. ortleppi was detected in only 5 faecal samples. We report for the first time the presence of E. felidis eggs in two dog faecal samples (from Maasai Mara region). Mixed infections of these taxa were also found in faecal samples, including: E. granulosus s. s. and E. canadensis (G6/7) (n = 7), E. granulosus s. s. and E. ortleppi (n = 1) and all three species (n = 1). The dog data presented here confirm the differences in diversity and abundance of Echinococcus spp. between regions of Kenya, correspond well with previously published data from livestock, and tentatively suggest a role of domestic dogs as a link between domestic and sylvatic cycles of Echinococcus spp.

Genetic differentiation of the G6/7 cluster of Echinococcus canadensis based on mitochondrial marker genes.

Among the genotype/species causing cystic echinococcosis, the taxonomic status of Echinococcus canadensis is only partially resolved. Within E. canadensis, four genotypes (G6, G7, G8 and G10) have been described based on short mitochondrial sequences, of which G6 and G7 (the 'camel' and the 'pig' strain, respectively) are closely related and variously regarded as microvariants of a single strain G6/7. Globally, this G6/7 cluster is the second most important agent of human cystic echinococcosis and is the predominant Echinococcus taxon in large parts of sub-Saharan Africa. To add data on the internal structure and the geographical distribution of this cluster, we analysed diversity and population structure of 296 isolates of E. canadensis from sub-Saharan Africa, the Middle East and Europe using the complete mitochondrial cytochrome c oxidase subunit 1 (cox1) (1,608bp) and NADH dehydrogenase subunit 1 (nad1) (894bp) gene sequences. Polymorphism of the mtDNA loci gave 51 (cox1), 33 (nad1) and 73 (cox1-nad1 concatenated) haplotypes. African and Middle Eastern isolates mainly grouped in a star-like structure around a predominant haplotype, while the European isolates produced more diversified networks. Although the cox1 diagnostic sequence for G6 is frequent in the African/Middle Eastern sub-cluster, and that for G7 is common in the European isolates, numerous intermediate variants prevent a clear distinction into 'G6' or 'G7', and the entire taxon is best treated as a common haplotype cluster G6/7. Meanwhile, the G6/7 cluster is clearly distinct from sequences of wildlife isolates of G8 and G10 from the northern hemisphere, and sequences of the latter genotypes were remarkably distant from each other. It is clear from the present study that, based on mitochondrial data, G6/7 is a coherent genotypic entity within E. canadensis that retains substantial intraspecific variance, and sub-populations share common ancestral polymorphisms and haplotypes. This study provides the basis for wider biogeographic comparison and population genetics studies of this taxon.

Invasive multidrug-resistant non-typhoidal Salmonella infections in Africa: zoonotic or anthroponotic transmission?

In Africa, multidrug-resistant non-typhoidal salmonellae (NTS) are one of the leading causes of morbidity and high mortality in children under 5 years of age, second in importance only to pneumococcal disease. The authors studied NTS isolates from paediatric admissions at two hospitals in Nairobi, Kenya, and followed the index cases to their homes, where rectal swabs and stools from parents and siblings, and from animals in close contact, were obtained. The majority of NTS obtained from cases were Salmonella enterica serotype Typhimurium (106 out of 193; 54.9%) and Salmonella enterica serotype Enteritidis (64; 33.2%), a significant proportion (34.2%) of which were multiply resistant to three or more antibiotics, including ampicillin, tetracycline, cotrimoxazole and chloramphenicol. Only 23.4% of NTS were fully susceptible to all 10 antibiotics tested. Of the 32 NTS obtained from contacts (nine adults and 23 children) at the homes of index cases, 21 (65.6%) isolates were similar by antibiotic-susceptibility profiles and plasmid content, and their XbaI- and SpeI-digested chromosomal DNA patterns were indistinguishable from those of the corresponding index cases. Only three out of 180 (1.7%) samples from environmental sources, including animals, soil, sewers and food, contained NTS matching those from corresponding index cases. The carriage of NTS in an asymptomatic population was represented by 6.9% of human contacts from 27 out of 127 homes sampled. This population of carriers may represent an important reservoir of NTS that would play a significant role in the epidemiology of community-acquired NTS bacteraemia in children.

Increasing prevalence of multidrug-resistant non-typhoidal salmonellae, Kenya, 1994-2003.

Over the last decade there has been a steady increase in the proportion of multidrug resistance among non-typhoidal salmonellae (NTS) isolated from adult patients with bacteraemia in Kenya. The prevalence of NTS multiply resistant to all commonly available drugs including ampicillin, streptomycin, co-trimoxazole, chloramphenicol and tetracycline rose from 31% in 1994 to 42% at present, with concomitantly higher MICs of each drug. Resistance is encoded on large self-transferable 100-110 kb plasmids. Pulsed field gel electrophoresis of XbaI and SpeI digested chromosomal DNA revealed three main digest patterns for Salmonella enterica serotype Typhimurium and two main patterns for Salmonella enterica serotype Enteritidis. Although the genotypes of NTS remained fairly stable over the last decade, the large increase in MICs of all commonly used drugs and increased MICs of ciprofloxacin, poses a major challenge for treatment of invasive NTS infection.