High MERS-CoV seropositivity associated with camel herd profile, husbandry practices and household socio-demographic characteristics in Northern Kenya.

Despite high exposure to Middle East respiratory syndrome coronavirus (MERS-CoV), the predictors for seropositivity in the context of husbandry practices for camels in Eastern Africa are not well understood. We conducted a cross-sectional survey to describe the camel herd profile and determine the factors associated with MERS-CoV seropositivity in Northern Kenya. We enrolled 29 camel-owning households and administered questionnaires to collect herd and household data. Serum samples collected from 493 randomly selected camels were tested for anti-MERS-CoV antibodies using a microneutralisation assay, and regression analysis used to correlate herd and household characteristics with camel seropositivity. Households reared camels (median = 23 camels and IQR 16-56), and at least one other livestock species in two distinct herds; a home herd kept near homesteads, and a range/fora herd that resided far from the homestead. The overall MERS-CoV IgG seropositivity was 76.3%, with no statistically significant difference between home and fora herds. Significant predictors for seropositivity (P ⩽ 0.05) included camels 6-10 years old (aOR 2.3, 95% CI 1.0-5.2), herds with ⩾25 camels (aOR 2.0, 95% CI 1.2-3.4) and camels from Gabra community (aOR 2.3, 95% CI 1.2-4.2). These results suggest high levels of virus transmission among camels, with potential for human infection.

Biological cost of tolerance to heavy metals in the mosquito Anopheles gambiae.

The global rate of heavy metal pollution is rapidly increasing in various habitats. Anopheles malaria vector species (Diptera: Culicidae) appear to tolerate many aquatic habitats with metal pollutants, despite their normal proclivity for 'clean' water (i.e. low levels of organic matter). Investigations were conducted to establish whether there are biological costs for tolerance to heavy metals in Anopheles gambiae Giles sensu stricto and to assess the potential impact of heavy metal pollution on mosquito ecology. Anopheles gambiae s.s. were selected for cadmium, copper or lead tolerance through chronic exposure of immature stages to solutions of the metals for three successive generations. Biological costs were assessed in the fourth generation by horizontal life table analysis. Tolerance in larvae to cadmium (as cadmium chloride, CdCl(2)), copper [as copper II nitrate hydrate, Cu(NO(3))(2) 2.5 H(2)O] and lead [as lead II nitrate, Pb(NO(3))(2)], monitored by changes in LC(50) concentrations of the metals, changed from 6.07 microg/L, 12.42 microg/L and 493.32 microg/L to 4.45 microg/L, 25.02 microg/L and 516.69 microg/L, respectively, after three generations of exposure. The metal-selected strains had a significantly lower magnitude of egg viability, larval and pupal survivorship, adult emergence, fecundity and net reproductive rate than the control strain. The population doubling times were significantly longer and the instantaneous birth rates lower in most metal-selected strains relative to the control strain. Our results suggest that although An. gambiae s.s. displays the potential to develop tolerance to heavy metals, particularly copper, this may occur at a significant biological cost, which can adversely affect its ecological fitness.