Decoys and Dilution: The Impact of Incompetent Hosts on Prevalence of Chagas Disease

Abstract

Biodiversity is commonly believed to reduce risk of vector-borne zoonoses. However, researchers already showed that the effect of biodiversity on disease transmission is not that straightforward. This study focuses on the effect of biodiversity, specifically on the effect of the decoy process (additional hosts distracting vectors from their focal host), on reducing infections of vector-borne diseases in humans. Here, we consider the specific case of Chagas disease and use mathematical population models to observe the impact on human infection of the proximity of chickens, which are incompetent hosts for the parasite but serve as a preferred food source for vectors. We consider three cases as the distance between the two host populations varies: short (when farmers bring chickens inside the home to protect them from predators), intermediate (close enough for vectors with one host to detect the presence of the other host type), and far (separate enclosed buildings such as a home and hen-house). Our analysis shows that the presence of chickens reduces parasite prevalence in humans only at an intermediate distance under the condition that the vector birth rate from feeding on chickens is sufficiently low..

Effectiveness of fluralaner treatment regimens for the control of canine Chagas disease: A mathematical modeling study

“…Here, we consider a model with a single vector-host population for the transmission of T. cruzi between triatomines and peridomestic dogs. Like most Chagas disease models [35,43,45,46,51,58], here we ignore the impact of seasonality on triatomine dynamics by assuming all model parameters to be constant over time. We used an age-structured model for the triatomine population (Fig 1).…”

“…Such efforts have identified reducing domestic vectorial transmission as key to reducing the incidence of Chagas disease in humans [43,44]. Further, housing animals-including dogs-in homes has been linked to an increased risk of T. cruzi infection in humans [4,45,46,47,48,49,50].…”

Impact of cattle on joint dynamics and disease burden of Japanese encephalitis and leptospirosis

“…During our literature review, we did not find any value for infection rates of leptospirosis in cattle and in humans (β lc and β lh respectively). Hence, we follow the method used in [20,19] to estimate β lc and β lh which gives…”

“…Hence, the presence of cattle increases host richness in the setting, which might eventually reduce the combined burden of these two diseases for humans. Earlier studies showed that an additional host (host richness) in a setting helps to reduce human infections of vector-borne diseases if certain conditions are maintained [16,17,18,20]. Johnson and Thieltges in 2010 identified that host diversity may help to reduce human infections depending on the relative abundance of additional host(s) relative to the focal host [16].…”

“…Recently in 2020, Zahid and Kribs showed that an additional host (dog, reservoir host) in a community can help in reducing the prevalence of visceral leishmaniasis in humans depending on the additional host's irritability to vector bites [18]. In another study, the same authors established that the presence of an additional host (chicken, incompetent host) in a domestic setting might help to reduce the prevalence of Chagas disease in humans if the distance between the two host populations (humans and chickens) is maintained at a certain range [20].…”