Rodent-Borne Bartonella Infection Varies According to Host Species Within and Among Cities

Abstract

It is becoming increasingly likely that rodents will drive future disease epidemics with the continued expansion of cities worldwide. Though transmission risk is a growing concern, relatively little is known about pathogens carried by urban rats. Here, we assess whether the diversity and prevalence of Bartonella bacteria differ according to the (co)occurrence of rat hosts across New Orleans, LA (NO), where both Norway (Rattus norvegicus) and roof rats (Rattus rattus) are found, relative to New York City (NYC) which only harbors Norway rats. We detected human pathogenic Bartonella species in both NYC and New Orleans rodents. We found that Norway rats in New Orleans harbored a more diverse assemblage of Bartonella than Norway rats in NYC and that Norway rats harbored a more diverse and distinct assemblage of Bartonella compared to roof rats in New Orleans. Additionally, Norway rats were more likely to be infected with Bartonella than roof rats in New Orleans. Flea infestation appears to be an important predictor of Bartonella infection in Norway rats across both cities. These findings illustrate that pathogen infections can be heterogeneous in urban rodents and indicate that further study of host species interactions could clarify variation in spillover risk across cities.

Rat Lungworm Infection in Rodents across Post-Katrina New Orleans, Louisiana, USA

“…Our overall estimate of 38% infection prevalence in New Orleans is comparable to count-based estimates reported for other areas where A. cantonensis is considered endemic ( 19 , 20 , but see 21 ). We also found A. cantonensis in rats across New Orleans and in neighboring St. Bernard Parish, which contrasts with the patchy distributions exhibited by other rodent-associated pathogens in cities ( 22 – 25 ). Although rat lungworm is present across New Orleans, infection prevalence varied according to geography and rodent host species, suggesting the risk for transmission to humans might be mediated in part by geographically variable landscape features that affect commensal rats ( 13 , 14 ).…”

“…Waugh et al ( 19 ) similarly reported differences in intensity and prevalence in rats from Jamaica according to size but not sex, although an earlier study found that female Norway rats were more likely to be infected ( 26 ). Evidence that A. cantonensis infection differs by host age contrasts with findings for other urban rodent–associated pathogens, including flea-vectored Bartonella bacteria ( 25 ). The finding of distinct Bartonella species in Norway rats and roof rats ( 25 ) suggests that co-occurrence does not facilitate pathogen transmission, whereas our results indicate otherwise.…”

“…Evidence that A. cantonensis infection differs by host age contrasts with findings for other urban rodent–associated pathogens, including flea-vectored Bartonella bacteria ( 25 ). The finding of distinct Bartonella species in Norway rats and roof rats ( 25 ) suggests that co-occurrence does not facilitate pathogen transmission, whereas our results indicate otherwise. Contrasting patterns in the demography of definitive host infection may reflect pathogen-specific differences in transmission pathways.…”

Bartonella Bacteria in Urban Rats: A Movement From the Jungles of Southeast Asia to Metropoles Around the Globe

“…Surprisingly, no Bartonella-positive rats were found in New York City among 87 rats cultured during the survey conducted by Ellis et al (1999). In two other studies conducted in five sites within New York City, 33% (25/133) R. norvegicus were Bartonella-positive by PCR (Firth et al, 2014) and 23% (30/133) by culturing (Peterson et al, 2017). Ellis et al (1999) described seven genotypes of Bartonella among 63 isolates obtained from R. norvegicus.…”

“…Interestingly, four rats from one location carried B. tribocorum, the bacterium dominant in rats in Los Angeles; whereas four Bartonella-positive rats from another location carried another bacterium, B. coopersplainsensis, originally described from Rattus leucopus in Australia (Gundi et al, 2009) and the most prevalent species in rats from New Zealand (Helan et al, 2018). In the U.S., this bacterium was found only in R. rattus from New Orleans (Peterson et al, 2017).…”