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

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. Electronic supplementary material The online version of this article (10.1007/s00436-020-06776-3) contains supplementary material, which is available to authorized users.

Intestinal Helminths in Wild Rodents from Native Forest and Exotic Pine Plantations (Pinus radiata) in Central Chile

“…We used traditional routine coprological analyses to detect helminths in feces, which have been successfully employed to address the effect of land use on parasites elsewhere [ 11 , 35 , 38 ]. However, further studies are needed to identify the helminth species present in the study area which should focus on identification of adult helminths [ 30 ] and/or species identification through molecular tools, which has been scarcely used for helminth egg identification from fecal samples of rodents [ 39 ].…”

A parasitological survey of zoonotic cestodes carried by house rats in Aswan, Egypt, reveals cryptic diversity at the molecular level

“…On the other hand, the present study detected a lower prevalence of H. taeniaeformis in rats than did similar studies in Argentina (39.5%) [33], Korea (33.8%) [34], and Grenada, West Indies (67.6%) [35]. Although the prevalence of helminth infection in rats varied between studies, these variations may be attributed to the differences in climatic conditions, environmental hygiene, previous control interference, socioeconomic status of the occupants, intermediate host abundance, and host vulnerability to parasite infection [2,36].…”

“…Rodent-borne helminthiases are neglected diseases that disproportionately affect (but are not limited to) residents of low-and middle-income countries. These cause a variety of health problems in humans, including malnutrition, increased prevalence of malaria and HIV/AIDS, decreased vaccine effectiveness, and increased incidence of allergies [2].…”

Enzootic Hepatic Capillariasis (Calodium hepaticum) in Street Rats (Rattus norvegicus) from Marseille City, France

“…Though few rat specimens were herein tested, which represent a limitation of the study, we cannot conclude about changing in the prevalence of this parasitosis. In other large cities, the prevalence in the urban rat population is variable, for example: 88% (176/201) in Baltimore (USA), 83% (337/402) in Salvador de Bahia (Brazil), 45% (33/74) in Rio de Janeiro (Brazil), 36% (241/671) in Vancouver (Canada), 26% (109/422) in Henan Province (China), 22% (21/97) in Kuala Lumpur (Malaysia), 20% (51/254) in Medellin (Colombia), 17% (17/100) in Barcelona (Spain) and 6% (18/302) in Belgrade (Serbia) [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ].…”