A population-dynamics simulation model of the main vectors of Chagas' Disease transmission, Thodnius prolixus and Triatoma infestans

Rabinovich, Jorge E.; Himschoot, Patricia

doi:10.1016/0304-3800(90)90019-d

Cited by 36 publications

(27 citation statements)

References 5 publications

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“…Indeed, compared to classical vector-borne disease models that assume that hosts are non-limiting and that are therefore only valid for low vector-host ratios [8,9], we considered here (following [10,11,12,13]) that hosts can be limiting as well, which should reasonably occur in Chagas' disease as hosts typically become irritable when vectors are too numerous [14]. This enabled us to find conditions under which the two parasite strains are differentially advantaged along the range of possible vector-host ratios.…”

Section: Discussionmentioning

confidence: 99%

“…In such models, the per-vector biting rate is always maximal and independent of the host-vector ratio, and the total contact rate only limited by vector density. Chagas' disease vectors, the Triatomines (see below), are however known to induce irritability in their hosts when the number of their bites is too high [14], which is likely to be the case among other vector-borne diseases.…”

Section: Introductionmentioning

confidence: 99%

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The role of the ratio of vector and host densities in the evolution of transmission modes in vector-borne diseases. The example of sylvatic Trypanosoma cruzi

Pelosse

Kribs-Zaleta

2012

Journal of Theoretical Biology

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Pathogens may use different routes of transmission to maximize their spread among host populations. Theoretical and empirical work conducted on directly-transmitted diseases suggest that horizontal (i.e., through host contacts) and vertical (i.e., from mother to offspring) transmission modes trade off, on the ground that highly virulent pathogens, which produce larger parasite loads, are more efficiently transmitted horizontally, and that less virulent pathogens, which impair host fitness less significantly, are better transmitted vertically. Other factors than virulence such as host density could also select for different transmission modes, but they have barely been studied. In vector-borne diseases, pathogen transmission rate is strongly affected by host-vector relative densities and by processes of saturation in contacts between hosts and vectors. The parasite Trypanosoma cruzi which is transmitted by triatomine bugs to several vertebrate hosts is responsible for Chagas' disease in Latin America. It is also widespread in sylvatic cycles in the southeastern U.S. in which it typically induces no mortality costs to its customary hosts. Besides classical transmission via vector bites, alternative ways to generate infections in hosts such as vertical and oral transmission (via the consumption of vectors by hosts) have been reported in these cycles. The two major T. cruzi strains occurring in the U.S. seem to exhibit differential efficiencies at vertical and classical horizontal transmissions. We investigated whether the vector-host ratio affects the outcome of the competition between the two parasite strains using an epidemiological two-strain model considering all possible transmission routes for sylvatic T. cruzi. We were able to show that the vector-host ratio influences the evolution of transmission modes providing that oral transmission is included in the model as a possible transmission mode, that oral and classical transmissions saturate at different vector-host ratios and that the vector-host ratio is between the two saturation thresholds. Even if data on parasite strategies and demography of hosts and vectors in the field are crucially lacking to test to what extent the conditions needed for the vector-host ratio to influence evolution of transmission modes are plausible, our results open new perspectives for understanding the specialization of the two major T. cruzi strains occurring in the U.S. Our work also provides an original theoretical framework to investigate the evolution of alternative transmission modes in vector-borne diseases.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The role of the ratio of vector and host densities in the evolution of transmission modes in vector-borne diseases. The example of sylvatic Trypanosoma cruzi

Pelosse

Kribs-Zaleta

2012

Journal of Theoretical Biology

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“…Basombrío et al 1993). They also lend realism to mathematical models of T. cruzi transmission, most of which assume that human and dog infectiousness are host age-independent and homogeneous within each host population (Rabinovich and Himschoot, 1990;Cohen and Gürtler, 2001). Depending on the local particular structure of domestic transmission, dogs and cats may have to be treated separately in mathematical models of transmission.…”

Section: Discussionmentioning

confidence: 99%

Domestic dogs and cats as sources ofTrypanosoma cruziinfection in rural northwestern Argentina

et al. 2006

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SUMMARYThe reservoir capacity of domestic cats and dogs for Trypanosoma cruzi infection and the hostfeeding patterns of domestic Triatoma infestans were assessed longitudinally in 2 infested rural villages in north-western Argentina. A total of 86 dogs and 38 cats was repeatedly examined for T. cruzi infection by serology and/or xenodiagnosis. The composite prevalence of infection in dogs (60%), but not in cats, increased significantly with age and with the domiciliary density of infected T. infestans. Dogs and cats had similarly high forces of infection, prevalence of infectious hosts (41-42%), and infectiousness to bugs at a wide range of infected bug densities. The infectiousness to bugs of seropositive dogs declined significantly with increasing dog age and was highly aggregated. Individual dog infectiousness to bugs was significantly autocorrelated over time. Domestic T. infestans fed on dogs showed higher infection prevalence (49%) than those fed on cats (39%), humans (38%) or chickens (29%) among 1085 bugs examined. The basic reproduction number of T. cruzi in dogs was at least 8·2. Both cats and dogs are epidemiologically important sources of infection for bugs and householders, dogs nearly 3 times more than cats.

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“…The existing mathematical models of the transmission of Chagas' disease do not explicitly include the existence of highly infective domestic animal reservoirs of T. cruzi and seasonality. 32,33 Because T. infestans feed preferentially and more frequently on dogs and chickens during the hot weather (thus boosting the bug population) and dogs are highly infective reservoirs, the combined effects of chickens, dogs, and cats on the domiciliary transmission dynamics may overwhelmingly dominate the contribution to transmission due solely to humans in settings such as the villages we studied.The methods developed in our study may be applied to other domiciliary triatomine species and other domestic animal reservoirs. For example, in some situations, 13, 34-36 rodents and opossums show long-lasting parasitemia 37, 38 and seem to play a role analogous to that of dogs in northwest Argentina.…”

mentioning

confidence: 99%

Influence of humans and domestic animals on the household prevalence of Trypanosoma cruzi in Triatoma infestans populations in northwest Argentina.

Gürtler¹,

Cohen²,

Cecere³

et al. 1998

The American Journal of Tropical Medicine and Hygiene

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Abstract. In three rural villages of northwest Argentina, the overall proportion of domiciliary Triatoma infestans infected with Trypanosoma cruzi was 49% among 1,316 bugs individually examined for infection in March and October 1992). Most of the variation among individual households in the proportion of infected triatomines was explained by variations among houses in the proportion of bugs that fed on dogs or cats, the prevalence of infected dogs or cats, and the proportion of bugs that fed on humans, according to a logistic multiple regression analysis. The effects of human infection rates on bug infection rates were not statistically significant. After adjusting for the effects of other predictors, the presence of chickens in bedroom areas had negative and significant effects on the proportion of infected Triatoma infestans, and positive and significant effects on the number of T. cruzi-infected triatomines collected per person-hr per house. Dog or cat infection rates and the proportion of bugs that fed on dogs or cats and on chickens explained 80% of the total variance of infected-bug numbers in a linear multiple regression model. This is the first study to use detailed field data to show that variations in triatomine infection rates depend on bug host feeding patterns and dog or cat infection rates, while the presence of chickens in bedroom areas exerts opposite effects on the proportion and number of infected triatomines. Domestic animals play a crucial role in the domiciliary transmission of T. cruzi.Triatoma infestans Klug, probably the most important and widespread domiciliary vector of Trypanosoma cruzi, 1 showed one of the highest rates of infection with T. cruzi (median ϭ 34%, range ϭ 12-68%) in extensive surveys carried out when insecticidal campaigns were nil or at an early stage in several countries. 2 For young men drafted into military service from all over Argentina, the Province of Santiago del Estero (northwest Argentina) had the highest prevalence rate of seropositivity for T. cruzi among all provincewide prevalence rates in the period 1964-1969 when the first screening took place, and the third highest prevalence rate in 1981. 3 In this province, the percentage of T. cruzi-infected Triatoma infestans collected from human sleeping quarters (hereafter domiciliary areas) was high (44%) and widely variable (range ϭ 21-82%) from district to district. 4 More recently, domiciliary vector infection rates were 31% more than 10 years after the first spraying of houses with insecticides in northwest Santiago del Estero. 5 Explaining such variable infection rates of domiciliary triatomines within a given community or province may increase our understanding of the transmission dynamics of T. cruzi.Vector feeding patterns link hosts, vectors, and the transmission of parasites in either direction between hosts and vectors. Dogs, chickens, and humans are the most important host blood sources of domiciliary Triatoma infestans throughout its range. 6 In northwest Argentina, the feeding pattern of domiciliar...

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A population-dynamics simulation model of the main vectors of Chagas' Disease transmission, Thodnius prolixus and Triatoma infestans

Cited by 36 publications

References 5 publications

The role of the ratio of vector and host densities in the evolution of transmission modes in vector-borne diseases. The example of sylvatic Trypanosoma cruzi

The role of the ratio of vector and host densities in the evolution of transmission modes in vector-borne diseases. The example of sylvatic Trypanosoma cruzi

Domestic dogs and cats as sources ofTrypanosoma cruziinfection in rural northwestern Argentina

Influence of humans and domestic animals on the household prevalence of Trypanosoma cruzi in Triatoma infestans populations in northwest Argentina.

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