Geographic Population Genetic Structure of the New World Screwworm, Cochliomyia hominivorax (Diptera: Calliphoridae), Using SNPs

Old World Screwworm myiasis: First report of auricular Chrysomya bezziana myiasis in a dog in Singapore

A German Shepherd dog was presented to a referral practice for screwworm myiasis affecting the ear. The successful management involved killing the larvae with afoxolaner plus milbemycin oxime and using video otoscopy to completely remove dead larvae. To the best of our knowledge, this is the first case report of auricular myiasis by Chrysomya bezziana in a dog in Singapore and the first report of video otoscopic management of myiasis.

Development of a diagnostic single nucleotide polymorphism (SNP) panel for identifying geographic origins of Cochliomyia hominivorax, the New World screwworm

The New World screwworm, Cochliomyia hominivorax, causes myiasis in livestock, humans, and other warm-blooded animals in much of South America and the Caribbean. It has been eradicated from North and Central America using the sterile insect technique and a biological barrier is currently maintained at the Panama - Colombian border. However, C. hominivorax is still a threat to eradicated areas as outbreaks can and do occur. In order to identify the origin of a fly involved in an outbreak scenario, diagnostic tools would be beneficial. Recently, the geographic population structure of this species was identified using single nucleotide polymorphisms (SNPs). Here we characterize the three major regional clusters: South America, the Inner Caribbean, and the Outer Caribbean. The objective of this study was to develop a SNP (single nucleotide polymorphism) panel to distinguish between these three clusters. A panel was developed using two unique SNPs per region for a total of six SNPs. This diagnostic SNP assay will allow for rapid source determination of flies from future incursions in order to intercept introductory pathways and aid in the control of New World screwworm.

Insights into the genetic landscape and presence of Cochliomyia hominivorax in the Caribbean

The New World screwworm, Cochliomyia hominivorax, is a major parasite that causes myiasis in livestock, humans, and other warm-blooded animals in the western hemisphere. There is a permanent biological border that is maintained between Panama and Colombia, as it has been eradicated from North and Central America. However, it still exists in much of the Caribbean and South America causing an estimated annual loss of $3.6 billion dollars in South America alone. Less information is available for C. hominivorax in the Caribbean. Thus, here we examined its presence and genetic landscape in order to gain insights into this fly's distribution in this region. First, through sampling efforts, novel GPS (Global Positioning System) coordinates were collected. Second, the environmental correlates of those presence points were examined. Next, samples were sequenced in order to obtain a pairwise Φ_IT genetic distance matrix. And lastly, this matrix was used to create a genetic landscape of divergence. The results of the genetic landscape show flies as more diverse in Trinidad and Tobago and less diverse in the Dominican Republic. This is perhaps due to the proximity of Trinidad to Venezuela and gene flow may be occurring between these two areas. This information will aid in screwworm surveillance and control programs by providing environmental correlates and a view into the distribution of these flies.