Mathematical modelling for Zoonotic Visceral Leishmaniasis dynamics: A new analysis considering updated parameters and notified human Brazilian data

Abstract

Brazil is one of the highest endemic countries for Zoonotic Visceral Leishmaniasis: according to the Brazilian Ministry of Health, the annual number of new human cases and deaths due to this disease has been increasing for the last 20 years. In addition, regarding the Americas, the specific relationship between canine and human for Visceral Leishmaniasis dynamics is still not well understood. In this work we propose a new model for Zoonotic Visceral Leishmaniasis, based on the models previously published by Burattini et al. (1998) and Ribas et al. (2013). Herein, we modeled the disease dynamics using a modified set of differential equations from those two authors, considering the same assumptions (inclusion of human, dog and sandfly populations, all constants over time). From this set of equations we were able to calculate the basic reproduction number scriptR0 and to analyze the stability and sensitivity of the system to the parameters variability. As main result, when the stability of the system is reached, the normalized reporting human cases rate is estimated in 9.12E-08/day. This estimation is very close to the 2015 report from Araçatuba city, 5.69E-08/day. We also observed from stability and sensitivity analysis that the activity of sandfly population is critical to introduction and maintenance of Zoonotic Visceral Leishmaniasis in the population. In addition, the importance of dog as source of infection concentrates on latent dog, since it does not show clinical symptoms and signs and, therefore, has a great contribution to disease dissemination. As conclusion, considering the presently ethical issues regarding to elimination of positive dog in Brazil and the highly sensitivity of disease dynamics on sandfly population, we recommend that the sandfly population control should be prioritized.

Canine serological survey and dog culling ant its relationship with Human ­Visceral leishmaniasis in an endemic urban area.

“…In addition to the technical issues, the most controversial aspect of canine reservoir elimination has been the ethical question considering the emotional involvement of both the owners and the subjects involved in the culling procedure [33][34][35][36][37][38][39][40][41][42][43][44][45][46]. However, it is noteworthy that HVL is a disease with high lethality if untreated, and it is in the process of geographical expansion [3,47].…”

“…The use of insecticide-impregnated collars has been recommended as the most effective measure among those cited above [43,[53][54][55]. Silva et al [56] demonstrated a reduction of 15% (p = 0.004) in Montes Claros, MG, Brazil, and 60% (p <0.001) in Fortaleza, CE, Brazil, in the vector population of captured.…”

Spatio-temporal modelling ofLeishmania infantuminfection among domestic dogs: a simulation study and sensitivity analysis applied to rural Brazil

“…Moreover, when comparing the respective sensitivity test values in three other sand fly-associated 230 parameter sets, sand fly bite rate (parameter ID 11), probability of a susceptible dog becoming 231 infected when bitten by an infected sand fly (parameter ID 13) and proportion of female sand flies 232 unobserved (parameter ID 15), in each case we found the median average infection prevalence 233 to differ by over 10% across the range of values tested ( Figure 6, panels (11,13,15)).…”

Leishmaniose visceral canina nos municípios de Araçatuba e Birigui, estado de São Paulo, Brasil

“…Da mesma forma, a modelagem matemática tem sido aplicada aos estudos das leishmanioses visando representar a forma como a infecção se espalha numa população, permitindo a avaliação e/ou criação, ainda que de forma teórica, de instrumentos que possam, essencialmente, auxiliar nas ações de prevenção e/ou controle da dispersão da doença em foco (COSTA et al 2012;SEVÁ et al, 2016;SHIMOZAKO et al, 2017a;SHIMOZAKO et al, 2017b;HUSSAINI et al, 2017). Nesse sentido, este projeto pretende ampliar a compreensão da dinâmica de transmissão da infecção e contribuir assim para uma melhor elaboração e/ou direcionamento de medidas de prevenção e controle em nível de saúde Pública, por meio da identificação de áreas prioritárias, da avaliação das coberturas das estratégias de controle químico e do reservatório canino, da observação de fatores associados à infecção canina e da verificação da efetividade da eutanásia como medidas de controle.…”