Ticks and Rickettsiae Associated with Wild Animals Sold in Bush Meat Markets in Cameroon.

Ticks are obligate blood-sucking parasites of wild animals and transmit many zoonotic microorganisms that can spread to domesticated animals and then to humans. In Cameroon, little is known about tick diversity among wildlife, especially for animals which are hunted for human consumption. Therefore, this survey was undertaken to investigate tick and Rickettsia species diversity parasitizing the wild animals sold in bush meat markets in Cameroon. In total, 686 ticks were collected and identified to the species level based on morphology, and some were genetically analyzed using the 16S rRNA gene. Eighteen tick species belonging to five genera were identified: Amblyomma spp. (Amblyomma compressum, Amblyomma flavomaculatum, and Amblyomma variegatum), Haemaphysalis spp. (Haemaphysalis camicasi, Haemaphysalis houyi, Haemaphysalis leachi, and Haemaphysalis parmata), Hyalomma spp. (Hyalomma nitidum, Hyalomma rufipes, and Hyalomma truncatum), Ixodes spp. (Ixodes rasus and Ixodes moreli), and Rhipicephalus spp. (Rhipicephalus guilhoni, Rhipicephalus moucheti, Rhipicephalus muhsamae, Rhipicephalus microplus, Rhipicephalus camicasi, and Rhipicephalus linnaei). In terms of Rickettsia important for public health, two Rickettsia spp., namely Rickettsia aeschlimannii and Rickettsia africae, were detected in Hyalomma spp. and Amblyomma spp., respectively. Distinct tick-pathogen patterns were present for divergent sequences of R. africae associated with exclusively A. variegatum vectors (type strain) versus vectors comprising A. compressum, A. flavomaculatum, and A. variegatum. This suggests possible effects of vector species population dynamics on pathogen population circulation dynamics. Furthermore, Candidatus Rickettsia africaustralis was detected for the first time in Cameroon in I. rasus. This study highlights the high diversity of ticks among wildlife sold in bush meat markets in Cameroon.

Widespread co-endemicity of Trypanosoma species infecting cattle in the Sudano-Sahelian and Guinea Savannah zones of Cameroon.

BACKGROUND: African animal trypanosomosis remains the major constraint of livestock production and livelihood of pastoral communities in Cameroon. Despite several decades of vector and parasite control efforts, it has not been eradicated. Alternative and sustainable control strategies require a sound knowledge of the local species, strains and vectors. In the Sudano-Sahelian and Guinea Savannah of Cameroon the prevalence and genetic diversity of trypanosomes infecting cattle was investigated by microscopy of cattle blood buffy coat and molecular methods using generic primers targeting parts of the internal transcribed spacer 1 (ITS-1) and encoded glycosomal glyceraldehyde 3-phosphate dehydrogenase-gene (gGAPDH). RESULTS: A total of 1176 randomly chosen cattle from five divisions in the Sudano-Sahelian and Guinea Savannah of Cameroon were examined. The overall prevalence of trypanosomes by microscopy was 5.9% (56/953) in contrast to 53.2% (626/1176) when molecular tools were used. This indicated a limited sensitivity of microscopy in subclinical infections with frequently low parasitemia. Three trypanosome species were identified by light microscopy: T. vivax (2.3%), T. brucei (3.7%) and T. congolense (3.0%), whereas five were identified by PCR, namely T. grayi/T. theileri (30.8%), T. vivax (17.7%), T. brucei (14.5%) and T. congolense (5.1%). Unexpected cases of T. grayi (n = 4) and T. theileri (n = 26) were confirmed by sequencing. Phylogenetic analysis of the gGAPDH revealed the presence of T. vivax, clade A and T. vivax clade C, which were co-endemic in the Faro et Deo division. T. grayi/T. theileri were the predominant species infecting cattle in tsetse free areas. In contrast, T. vivax, T. brucei and T. congolense were more abundant in areas where the Glossina-vectors were present. CONCLUSIONS: The abundance of pathogenic trypanosomes in tsetse infested areas is alarming and even more, the occurrence of T. vivax, T. brucei, T. congolense, T. theileri and T. grayi in tsetse-free areas implies that tsetse control alone is not sufficient to control trypanosomosis in livestock. To implement control measures that reduce the risk of spread in tsetse free areas, close monitoring using molecular tools and a thorough search for alternative vectors of trypanosomes is recommended.

Onchocerca - infected cattle produce strong antibody responses to excretory-secretory proteins released from adult male Onchocerca ochengi worms.

BACKGROUND: The front line molecules from filarial worms and other nematodes or helminthes are their Excretory-Secretory (ES) products. Their interaction with the host cells, proteins and immune system accounts for the skin and eye pathology or hyposensitivity observed in human onchocerciasis. ES products and adult worms' crude extracts from Onchocerca ochengi, a filarial nematode that infects the African zebu cattle, were utilized in the present study as a model for studying Onchocerca volvulus that causes river blindness in man. METHODS: The ES products were generated from adult male and female worms in vitro and analyzed with poly acrylamide gel electrophoresis (PAGE) and enzyme-linked immunosorbent assay (ELISA) using sera from Onchocerca-infected cattle and humans. The cattle sera were collected from a herd that had been exposed for six years to natural transmission of Onchocerca spp. The expressed reactivity was evaluated and differences analyzed statistically using Kruskal-Wallis rank and Chi-square tests. RESULTS: The gel electrophoretic analyses of 156 ES products from O. ochengi female and male worms and of two somatic extracts from three females and 25 males revealed differences in the protein pattern showing pronounced bands at 15, 30-50 and 75 kDa for male ES proteins and 15, 25 and 40-75 kDa for somatic extracts, respectively and less than 100 kDa for female worms. Proteins in the ES products and somatic extracts from female and male Onchocerca ochengi worms were recognized by IgG in sera from both Onchocerca-exposed cattle and humans. Bovine serum antibodies reacted more strongly with proteins in the somatic extracts than with those in the ES products. Interestingly, the reaction was higher with male ES products than with ES products from female worms, suggesting that the males which migrate from one nodule to another are more exposed to the host immune system than the females which remain encapsulated in intradermal nodules. CONCLUSIONS: This study demonstrates that O. ochengi ES products and, in particular, extracts from male filariae may represent a good source of immunogenic proteins and potential vaccine candidates.

Comparative analysis of macrophage migration inhibitory factors (MIFs) from the parasitic nematode Onchocerca volvulus and the free-living nematode Caenorhabditis elegans.

The macrophage migration inhibitory factors (MIFs) from the filarial parasite Onchocerca volvulus (OvMIF) were compared to the MIFs from the free-living nematode Caenorhabditis elegans (CeMIF) with respect to molecular, biochemical and immunological properties. Except for CeMIF-4, all other MIFs demonstrated tautomerase activity. Surprisingly, OvMIF-1 displayed oxidoreductase activity. The strongest immunostaining for OvMIF-1 was observed in the outer cellular covering of the adult worm body, the syncytial hypodermis; moderate immunostaining was observed in the uterine wall. The generation of a strong humoral immune response towards OvMIF-1 and reduced reactivity to OvMIF-2 was indicated by high IgG levels in patients infected with O. volvulus and cows infected with the closely related Onchocerca ochengi, both MIFs revealing identical amino acid sequences. Using Litomosoides sigmodontis-infected mice, a laboratory model for filarial infection, MIFs derived from the tissue-dwelling O. volvulus, the rodent gut-dwelling Strongyloides ratti and from free-living C. elegans were recognized, suggesting that L. sigmodontis MIF-specific IgM and IgG1 were produced during L. sigmodontis infection of mice and cross-reacted with all MIF proteins tested. Thus, MIF apparently functions as a target of B cell response during nematode infection, but in the natural Onchocerca-specific human and bovine infection, the induced antibodies can discriminate between MIFs derived from parasitic or free-living nematodes.

Functional characterization and immune recognition of the extracellular superoxide dismutase from the human pathogenic parasite Onchocerca volvulus (OvEC-SOD).

Onchocerca volvulus is a human pathogenic filarial nematode causing chronic onchocerciasis, a disease characterized by chronic skin and eye lesions. Despite attempts to control this infection from many perspectives, it still remains a threat to public health because of adverse effects of available drugs and recent reports of drug resistance. Under control of an intact immune system, O. volvulus survives for a long time in the host by employing a variety of strategies including the utility of antioxidant enzymes. In the present study, we focus on the extracellular superoxide dismutase from O. volvulus (OvEC-SOD) found in the excretory/secretory products of adult worms. Contrary to previous studies, the OvEC-SOD was found to have a 19 amino acid long signal peptide that is cleaved off during the process of maturation. To validate this result, we designed a novel method based on Caenorhabditis elegans cup5(ar465) mutants to specifically evaluate signal peptide-mediated secretion of nematodal proteins. Following purification, the recombinant OvEC-SOD was active as a dimer. Site-directed mutagenesis of the three cysteines present in the OvEC-SOD shows that enzyme activity is markedly reduced in the Cys-192 mutant. A homology model of the OvEC-SOD underlines the importance of Cys-192 for the stabilization of the adjacent active site channel. The generation of a humoral immune response to secretory OvEC-SOD was indicated by demonstrating IgG reactivity in sera from patients infected with O. volvulus while the cross-reactivity of IgG in plasma samples from cows, infected with the most closely related parasite Onchocerca ochengi, occurred only marginally. High IgG1 and IgM titres were recorded in sera from mice infected with the filaria Litomosoides sigmodontis, however, low or no cellular proliferative responses were observed. Thus, the present data suggest that secretory OvEC-SOD is a target of the humoral immune response in human onchocerciasis and induced strongest IgG responses in hyperreactive onchocerciasis. Furthermore, humoral response during murine infection induced SOD-specific IgG that cross-reacted with OvEC-SOD.