Trypanosoma cruzi TcIII / Z3 genotype as agent of an outbreak of Chagas disease in the Brazilian Western Amazonia

Chagas’ disease is an emerging and neglected disease in the Brazilian Amazon region, where T. cruzi I predominates among the acute cases of the disease; and T. cruzi III/Z3, a population cluster from sylvatic areas of the Amazon basin, is rarely associated with human infections. On 23rd April 2007, the Foundation for Health Surveillance of the State of Amazonas, Brazil reported an outbreak of acute Chagas disease in the municipality of Coari on the Solimões River banks. Fresh blood examination confirmed the infection in 25 patients. Parasite culture in LIT medium was successful for 18 isolates. Molecular characterization was performed by PCR of the non‐transcribed spacer of the mini‐exon and by sequencing of the mitochondrial cytochrome c oxidase subunit II (COII) gene. The T. cruzi isolates were all from genotype Z3, and sequencing revealed that all isolates had equal COII sequences compatible with TcIII type, suggesting a single source of infection. To our knowledge, this is the first outbreak of acute cases caused uniquely by the genotype TcIII/Z3. Wild vectors harbouring TcIII stocks contribute to transmission when the triatomine species reaches human food chain or when humans invade the forest environment, where sylvatic cycle constitutes a reservoir of parasites that might be associated with specific epidemiological and clinical traits of the emergent Chagas disease in the Amazon.     

Costs of dengue prevention and incremental cost of dengue outbreak control in Guantanamo, Cuba

Objective To assess the economic cost of routine Aedes aegypti control in an at‐risk environment without dengue endemicity and the incremental costs incurred during a sporadic outbreak. Methods The study was conducted in 2006 in the city of Guantanamo, Cuba. We took a societal perspective to calculate costs in months without dengue transmission (January–July) and during an outbreak (August–December). Data sources were bookkeeping records, direct observations and interviews. Results The total economic cost per inhabitant (p.i.) per month. (p.m.) increased from 2.76 USD in months without dengue transmission to 6.05 USD during an outbreak. In months without transmission, the routine Aedes control programme cost 1.67 USD p.i. p.m. Incremental costs during the outbreak were mainly incurred by the population and the primary/secondary level of the healthcare system, hardly by the vector control programme (1.64, 1.44 and 0.21 UDS increment p.i. p.m., respectively). The total cost for managing a hospitalized suspected dengue case was 296.60 USD (62.0% direct medical, 9.0% direct non‐medical and 29.0% indirect costs). In both periods, the main cost drivers for the Aedes control programme, the healthcare system and the community were the value of personnel and volunteer time or productivity losses. Conclusions Intensive efforts to keep A. aegypti infestation low entail important economic costs for society. When a dengue outbreak does occur eventually, costs increase sharply. In‐depth studies should assess which mix of activities and actors could maximize the effectiveness and cost‐effectiveness of routine Aedes control and dengue prevention.