Are scavengers good for your health?: The effect of scavengers on disease transmission

Mitchell John Le Sage

doi:10.7273/000003959

Scavenging of infectious carcasses by heterospecific organisms may play an important, but insufficiently understood, role in disease transmission. Infected carcasses can be a major source of new infections in wildlife. In cases where diseases can cause an accumulation of infectious carcasses, a robust scavenging community could reduce the ability of the carcasses to cause new infections by quickly removing infected tissue. Alternatively, scavengers could exacerbate the spread of diseases by exposing susceptible organisms to infectious tissue. Identifying the role of scavengers in disease transmission is a crucial part of understanding the broader community interactions in disease systems. We carried out a study to determine the efficiency of scavenging invertebrates to remove carcass material from larval Long-toed Salamanders (Ambystoma macrodactylum), and investigated the effect of scavenging by an efficient larval invertebrate (Family: Dytiscidae) on the transmission of Frog Virus 3 (Genus: Ranavirus, Family: Iridoviridae) from carcasses. The feasibility of scavenging in the wild having an effect on carcass persistence, and therefore transmission, was estimated using the maximum scavenging efficiency of Dytiscidae larva from their functional response to carcass density, and using field survey counts to estimate relative densities of Dytiscidae larvae and A. macrodactylum in two ponds. We found that at least two families of invertebrates will scavenge readily on larval A. macrodactylum, (Dytiscidae and Aeshnidae). Using Dytiscidae larvae, we showed that scavenging on the carcass caused a significant decrease (44.5%) in the proportion of new infections caused by contact with a carcass, and that efficient scavenging has a similar effect on new infections as a physical barrier preventing naïve individuals from contacting a carcass. There was no evidence that scavenging increases infections indirectly through the water. An estimation of the potential effect of scavenging in two ponds showed that the maximum ability of the Dytiscidae to remove salamander carcasses varies through time and across ponds, but in at least some ponds, the scavengers would not be clearly overwhelmed by carcass density. Our results suggest that scavenging negatively influences disease transmission from carcasses, and this could potentially scale up to the population-level.

Are scavengers good for your health?: The effect of scavengers on disease transmission

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