Feline immunodeficiency virus in puma: Estimation of force of infection reveals insights into transmission

Abstract

Determining parameters that govern pathogen transmission (such as the force of infection, FOI), and pathogen impacts on morbidity and mortality, is exceptionally challenging for wildlife. Vital parameters can vary, for example across host populations, between sexes and within an individual's lifetime. Feline immunodeficiency virus (FIV) is a lentivirus affecting domestic and wild cat species, forming species‐specific viral–host associations. FIV infection is common in populations of puma (Puma concolor), yet uncertainty remains over transmission parameters and the significance of FIV infection for puma mortality. In this study, the age‐specific FOI of FIV in pumas was estimated from prevalence data, and the evidence for disease‐associated mortality was assessed. We fitted candidate models to FIV prevalence data and adopted a maximum likelihood method to estimate parameter values in each model. The models with the best fit were determined to infer the most likely FOI curves. We applied this strategy for female and male pumas from California, Colorado, and Florida. When splitting the data by sex and area, our FOI modeling revealed no evidence of disease‐associated mortality in any population. Both sex and location were found to influence the FOI, which was generally higher for male pumas than for females. For female pumas at all sites, and male pumas from California and Colorado, the FOI did not vary with puma age, implying FIV transmission can happen throughout life; this result supports the idea that transmission can occur from mothers to cubs and also throughout adult life. For Florida males, the FOI was a decreasing function of puma age, indicating an increased risk of infection in the early years, and a decreased risk at older ages. This research provides critical insight into pathogen transmission and impact in a secretive and solitary carnivore. Our findings shed light on the debate on whether FIV causes mortality in wild felids like puma, and our approach may be adopted for other diseases and species. The methodology we present can be used for identifying likely transmission routes of a pathogen and also estimating any disease‐associated mortality, both of which can be difficult to establish for wildlife diseases in particular.

Host relatedness and landscape connectivity shape pathogen spread in a large secretive carnivore

“…FIV pco is a rapidly evolving retrovirus 23 endemic to puma populations, and is thought to be predominantly transmitted horizontally via aggressive encounters 24 , although vertical transmission has been documented by phylogenetic analyses 25 . Because FIV pco is essentially apathogenic in puma 26, 27 , it is an ideal model pathogen to understand transmission dynamics in wild systems without potential confounding effects of disease on behaviour and demography 25, 28 . We examine what factors impact FIV pco spread using a novel pipeline synthesizing phylodynamic, phylogeographic and landscape genetic techniques (an ecophylogenetic approach 29 ).…”

Transmission of one predicts another: Apathogenic proxies for transmission dynamics of a fatal virus

“…Surprisingly, sex was not a significant predictor of FIV transmission. FIV force of infection is generally higher in male panthers, likely due to their increased fighting behaviors (71). However, studies in other felid species have found mixed importance of sex for FIV transmission, ranging from little to no importance (puma in the western United States: 72; bobcat: 73) to importance only among certain FIV subtypes (African lions: 74).…”

Targeted sampling reduces the uncertainty in force of infection estimates from serological surveillance

“…These approaches are applied after anesthetizing or killing the animals, and it is challenging to apply them to endangered animal species for their conservation. Some of their ages were obtained by tracking the animals from birth ( 17 ). Furthermore, measurement of size, weight, gum line recession, wear of a tooth, and tail length ( 18 , 19 ) can be used to estimate the age of animals.…”