Biocontrol of rats in an urban environment in Southeast Asia using Sarcocystis singaporensis

Abstract

BACKGROUND: Upon request of the local administration a control campaign targeting commensal rats (Rattus rattus, R. exulans) was conducted in 30 sub-districts (villages) of the World Heritage town Luang Prabang, Northern Laos, using rat bait containing lethal quantities of the parasitic protist Sarcocystis singaporensis. The associated investigations assessed the short-term control efficacy, willingness of residents to co-operate (community approach), and temporal and spatial changes of the urban rat population in response to treatment. RESULTS: Biological rodent control significantly reduced rodent activity (percentage of positive tracking patches) in the town, from a mean of 25.3% (±12.8% SD) before (January-February) down to 8.0% (±4.4%) after (June) treatment. Reduction of rodent activity relative to three untreated villages was 83%. Similarly, residents observed significantly fewer rats on their properties after the campaign (mean percentage of households (HHs) per village with sightings), whereby reduction of sightings amounted to 57%. There was significant correlation between residents' observation rates and rodent activity. Among 94 rats trapped before and after treatment each, proportions of adult R. exulans and juvenile R. rattus were higher after rodent control, suggesting that a considerable part of the adult house rat population had been removed. Furthermore, a 5% post-campaign incidence of infection suggested that few rats had survived bait uptake. CONCLUSION: S. singaporensis may be used successfully as tactical biocontrol agent for culling of rats in urban environments. We propose additional components of a long-term rodent management strategy for the town, without which the impact of culling campaigns would be limited.

Sarcocystis Species (Apicomplexa, Eucoccidiorida) Parasitizing Snakes

“…and to the short-tailed bandicoot rat (Nesokia indica) [14]. Due to its pathogenicity to IH, S. singaporensis was tested as an efficient biocontrol agent for non-native rats [14,15,94].…”

Reconsidering the “War on Rats”: What We Know From Over a Century of Research Into Municipal Rat Management

“…Later, Davis (1952) experimentally demonstrated how sanitation procedures (e.g., removing clutter, junk, and garbage) could sustainably reduce rat infestations in several city blocks. Other studies focused on the application of lethal methods, such as rodenticides (Drummond, 1970;Bajomi, 1980;Al-Sanei et al, 1984), introducing a pathogen into the rat population (Jäkel et al, 2019), and traps (Taylor et al, 2008). For example, Bajomi (1980) applied rodenticide to all properties across the entire city of Budapest, Hungary and then maintained application in active areas through subsequent decades (Bajomi et al, 2013).…”

Sarcocystis sp. shed by the common boa snake (Boa constrictor) in Brazil

“…that infect snakes, S. singaporensis and S. nesbitti have attracted special attention of the scientific community due to their impact in public health. The former uses the reticulated pythons ( Malayopython reticulatus ) as definitive hosts, and rodents of the genus Rattus and Bandicota as intermediate hosts; sporocysts of S. singaporensis have an interesting action as a natural rodenticide ( Jakel et al, 1996 , 2019 ); when high doses of sporocysts are ingested by rats, they usually die ( Zaman and Colley, 1975 ; Brehm and Frank, 1980 ; Jakel et al, 1996 ). S. nesbitti was reported as the causative agent of muscular sarcocystosis in humans in the southeast of Asia ( Abubakar et al, 2013 ; Italiano et al, 2014 ; Lau et al, 2014 ) and was firstly described as forming sarcocysts in a non-human primate ( Macaca mulata ) ( Mandour, 1969 ).…”