Leptospira Seroprevalence Detection and Rabies Virus Absence in an Urban Raccoon (Procyon lotor) Population in a Highly Populated Area, Costa Rica

Passive epidemiological surveillance in wildlife in Costa Rica identifies pathogens of zoonotic and conservation importance

Epidemiological surveillance systems for pathogens in wild species have been proposed as a preventive measure for epidemic events. These systems can minimize the detrimental effects of an outbreak, but most importantly, passive surveillance systems are the best adapted to countries with limited resources. Therefore, this research aimed to evaluate the technical and infrastructural feasibility of establishing this type of scheme in Costa Rica by implementing a pilot program targeting the detection of pathogens of zoonotic and conservation importance in wildlife. Between 2018 and 2020, 85 carcasses of free-ranging vertebrates were admitted for post-mortem and microbiology analysis. However, we encountered obstacles mainly related to the initial identification of cases and limited local logistics capacity. Nevertheless, this epidemiological surveillance scheme allowed us to estimate the general state of health of the country’s wildlife by establishing the causes of death according to pathological findings. For instance, 60% (51/85) of the deaths were not directly associated with an infectious agent. Though in 37.6% (32/85) of these cases an infectious agent associated or not with disease was detected. In 27.1% (23/85) of the cases, death was directly related to infectious agents. Furthermore, 12.9% (11/85), the cause of death was not determined. Likewise, this wildlife health monitoring program allowed the detection of relevant pathogens such as Canine Distemper Virus, Klebsiella pneumoniae, Angiostrongylus spp., Baylisascaris spp., among others. Our research demonstrated that this passive surveillance scheme is cost-effective and feasible in countries with limited resources. This passive surveillance can be adapted to the infrastructure dedicated to monitoring diseases in productive animals according to the scope and objectives of monitoring wildlife specific to each region. The information generated from the experience of the initial establishment of a WHMP is critical to meeting the challenges involved in developing this type of scheme in regions with limited resources and established as hotspots for emerging infectious diseases.

Prevalence and risk factors of Leptospira infection in urban brown rats (Rattus norvegicus), Vienna, Austria

Leptospirosis is a worldwide bacterial zoonosis which incidence is expected to increase in conjunction with global change. In urban ecosystems, synanthropic rats are the key source of Leptospira infection in humans and other animals. Risk assessment and prediction of human leptospirosis require investigations of the environment associated with the bacteria and infection patterns in the reservoir hosts. The objective of this study was to address the prevalence of mixed Leptospira infection in the lungs and kidneys of brown rats captured in three sites of the city centre of Vienna, Austria, between 2016 and 2018. A total of 96 brown rats were examined for the presence of Leptospira using PCR. Occurrence of mixed Leptospira infections was explored through next-generation sequencing (NGS). A logistic regression model was built to predict the individual infection status using morphological and land-use data. Overall, the prevalence of Leptospira interrogans in the kidney was 25% but varied among sites (0–36%). We did not evidence any pulmonary nor mixed infections. Host body mass and sex were strong predictors of Leptospira carriage in the sampled rats (relative variable importance (RVI) = 0.98 and 0.89, respectively) while the presence of water affected it moderately (RVI = 0.44). Our findings demonstrate that NGS is an unbiased approach to the direct characterisation of mixed leptospiral infections that could provide further insights into the ecology of Leptospira. Future surveillance programmes should consider the use of rats as sentinels for the early detection of emerging pathogenic Leptospira in urban ecosystems.