Evolutionary implications for interactions between multiple strains of host and parasite

Zhang, Pei; Sandland, Gregory J.; Feng, Zhilan; Xu, Da; Minchella, Dennis J.

doi:10.1016/j.jtbi.2007.05.011

Cited by 35 publications

(32 citation statements)

References 33 publications

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“…The basic reproductive number for a given strain, a familiar and key quantity in mathematical epidemiology, gives the mean number of secondary infections produced by a single infected individual (host or vector) introduced into a completely naive population. The invasion reproductive number (IRN) gives instead the mean number of secondary infections of the given strain produced by a single infected individual introduced into a population in which the other strain is already endemic [8,34,51]. In a cross-immunity context, therefore,R j < R j .…”

Section: Model Dynamicsmentioning

confidence: 99%

The role of adaptations in two-strain competition for sylvaticTrypanosoma cruzitransmission

Kribs-Zaleta¹,

Mubayi²

2012

Journal of Biological Dynamics

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This study presents a continuous-time model for the sylvatic transmission dynamics of two strains of Trypanosoma cruzi enzootic in North America, in order to study the role that adaptations of each strain to distinct modes of transmission (classical stercorarian transmission on the one hand, and vertical and oral transmission on the other) may play in the competition between the two strains. A deterministic model incorporating contact process saturation predicts competitive exclusion, and reproductive numbers for the infection provide a framework for evaluating the competition in terms of adaptive trade-off between distinct transmission modes. Results highlight the importance of oral transmission in mediating the competition between horizontal (stercorarian) and vertical transmission; its presence as a competing contact process advantages vertical transmission even without adaptation to oral transmission, but such adaptation appears necessary to explain the persistence of (vertically-adapted) T. cruzi IV in raccoons and woodrats in the southeastern United States.

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Section: Model Dynamicsmentioning

confidence: 99%

The role of adaptations in two-strain competition for sylvaticTrypanosoma cruzitransmission

Kribs-Zaleta¹,

Mubayi²

2012

Journal of Biological Dynamics

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“…The basic reproductive number for a given strain gives the mean number of secondary infections produced by a single infected individual (host or vector) introduced into a completely susceptible population. The invasion reproductive number (IRN) gives instead the mean number of secondary infections of the given strain produced by a single infected individual introduced into a population in which the other strain is already endemic [35,36]. In a cross-immunity context, therefore,R i < R i .…”

Section: Analysis and Reproductive Numbersmentioning

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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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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“…In order to identify new microbial targets and develop more effective antifungal therapies, it is important to understand the cellular and molecular mechanisms of the disease [6]. Recently, the implications of evolution for host-parasite interactions have led authors to investigate how heterogeneities in parasite virulence and host life-history may affect the persistence and spread of diseases in natural systems [7]. On the other hand, new virulence factors are being identified in many infectious microbes, and some research focuses on the relative contributions of virulence factors to pathogenesis [7,8].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, the implications of evolution for host-parasite interactions have led authors to investigate how heterogeneities in parasite virulence and host life-history may affect the persistence and spread of diseases in natural systems [7]. On the other hand, new virulence factors are being identified in many infectious microbes, and some research focuses on the relative contributions of virulence factors to pathogenesis [7,8]. The characterization of some of these factors has demonstrated that virulence is complex and multifactorial [9].…”

Section: Introductionmentioning

confidence: 99%

Interactions of Paracoccidioides brasiliensis with host cells: recent advances

Mendes-Giannini

Silva

et al. 2007

Mycopathologia

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Evolutionary implications for interactions between multiple strains of host and parasite

Cited by 35 publications

References 33 publications

The role of adaptations in two-strain competition for sylvaticTrypanosoma cruzitransmission

The role of adaptations in two-strain competition for sylvaticTrypanosoma cruzitransmission

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

Interactions of Paracoccidioides brasiliensis with host cells: recent advances

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