Helminths of urban rats in developed countries: a systematic review to identify research gaps

Diana S Gliga,Chris Walzer,Amélie Desvars-Larrive,Benoît Pisanu

doi:10.1007/s00436-020-06776-3

Abstract

Although black (Rattus rattus) and brown (Rattus norvegicus) rats are among the most widespread synanthropic wild rodents, there is a surprising scarcity of knowledge about their ecology in the urban ecosystem. In particular, relatively few studies have investigated their helminth species diversity in such habitat. We followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guideline to synthesize the existing published literature regarding the helminth fauna of urban rats in developed countries (North America, Europe, Australia, New Zealand and Japan). We aimed at describing the species diversity and richness of urban rat helminths, the species prevalence and associations, the methods of investigation, the pathological changes observed in the hosts, the risk factors of infection and the public health significance of rat-borne helminthiases. Twenty-three scientific papers published between 1946 and 2019 were reviewed, half of them were conducted in Europe. Twenty-five helminth species and eight genera were described from the liver, digestive tract, lungs and muscles of urban rats. The most commonly reported parasite was Calodium hepaticum. Prevalence and risk factors of helminth infection in urban rats varied greatly between studies. Observed pathological findings in the rat host were generally minor, except for C. hepaticum. Several rat helminths can parasitize humans and are therefore of public health significance. The lack of references to identification keys and the rare use of molecular tools for species confirmation represent the main limitation of these studies. Knowledge gap on this topic and the needs for future research are discussed.

Highlights

IntroductionWithin the fragmented urban ecosystem, modified habitat structures, increased resource availability, reduced biodiversity and altered trophic interactions affect wildlife population biology, the nature and functioning of wildlife communities (Bradley and Altizer 2007; Cavia et al 2009; Horsák et al 2013; Aronson et al 2016)
We addressed the following questions: 1) Which helminth species infect urban rats and what are their prevalence?
Two of them were removed because they were not conducted in developed countries, one was excluded because it did not investigate R. rattus or R. norvegicus, three were excluded because they were not conducted in urban settings and two were excluded because prevalence could not be extracted from the results

Summary

Introduction

Within the fragmented urban ecosystem, modified habitat structures, increased resource availability, reduced biodiversity and altered trophic interactions affect wildlife population biology, the nature and functioning of wildlife communities (Bradley and Altizer 2007; Cavia et al 2009; Horsák et al 2013; Aronson et al 2016). These changes are subsequently affecting host-parasites interactions, parasite transmission and the structure of the parasite communities (Bradley and Altizer 2007; Cable et al 2017), potentially leading to an augmented risk of spillover of wildlife parasites to humans (Gordon et al 2016). They can impact human nutritional status, inducing negative effects at different stages of the human life cycle (Crompton and Nesheim 2002), exacerbate malaria and HIV/AIDS, impair vaccine efficacy (World Health Organization 2012) and enhance the risk of allergy (Sitcharungsi and Sirivichayakul 2013)

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Results

Conclusion