Culex restuans Theobold, a putative vector of West Nile virus among birds in northern North America, also may serve as a bridge vector to mammals. Despite its potential public health importance, little is known about what regulates populations of this species. Mosquitoes generally are subject to both density-dependent reductions in survival and growth and to density-independent limitations on their population abundances. The mechanisms by which density dependence may occur in this species were examined in both field and laboratory studies. Nutrient-dependent reductions in growth were found in field studies. Under laboratory conditions, nutrient levels in larval habitats and total water volume per container contributed to survival and growth of larvae. We related these findings to density-independent changes in available habitat for larval development observed in other studies. These results may suggest a mechanism for patterns of mosquito abundance.

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Abstract. Risk factors for progression from acute malaria to multiple organ dysfunction syndrome (MODS) are poorly understood. The MODS is commonly diagnosed with the sequential organ failure assessment (SOFA) scale, but this scale has been understudied in patients with severe malaria. We conducted a cohort study among 426 adult males admitted to hospital with malaria in Bogotá, Colombia. We estimated SOFA scores and relative risks (RRs) for MODS during hospitalization according to patients' characteristics on admission. Risk of MODS was 7.3% over a median 6.0 days in hospital. Baseline hemoglobin was strongly, inversely associated with MODS (adjusted RR for hemoglobin 8.5 g/dL versus hemoglobin 11 g/dL = 9.5, 95% confidence interval [CI]: 3.6, 25.3). Plasmodium falciparum malaria and parasitemia were positively associated with MODS. There was a strong interaction between baseline parasitemia and hemoglobin on MODS risk. In conclusion, the use of parasitemia and hemoglobin on admission to identify high-risk patients deserves consideration.