Stomoxysflies (Diptera, Muscidae) are competent vectors of multiple livestock hemopathogens
Authors: Muita Julia W. , Bargul Joel L. , Makwatta JohnMark O. , Ngatia Ernest M. , Tawich Simon K. , Masiga Daniel K. , Getahun Merid N. 
Published: October 2024

Stomoxysflies are widely distributed and economically significant vectors of various livestock pathogens of veterinary importance. However, the role ofStomoxysspp. in pathogen transmission is poorly understood. Therefore, we studied the feeding patterns of these blood feeders collected from specific locations in Kenya, to identify various vertebrate hosts they fed on, and the livestock hemopathogens they carried, to elucidate their role in pathogens transmission. Our findings show that field-collectedStomoxysflies carried several pathogens includingTrypanosomaspp.,Anaplasmaspp., andTheileriaspp. that were also found in the blood of sampled livestock, namely camels and cattle. The findings on blood meal analysis show thatStomoxysflies fed on a variety of domestic and wild vertebrate hosts. We further determined whetherStomoxysspp. are vectors of hemopathogens they harbored by studying the vector competence ofS. calcitrans, S. niger niger,andS. bouetispecies complex, through laboratory and natural experimentalin vivostudies. We show that in the process of blood feedingStomoxysspp. complexes can transmitT. evansi(8.3%) andT. vivax(30%) to Swiss white mice. In addition, field-collectedStomoxyspp. were exposed to healthy mice for blood meal acquisition, and in the process of feeding, they transmittedTheileria mutansandAnaplasmaspp. to Swiss white mice (100% infection in the test mice group). All mice infected with both trypanosomes via stomoxys bite died while those infected withTheileriaandAnaplasmaspecies did not, demonstrating virulence difference between pathogens. The key finding of this study showing broad feeding host range, cosmopolitan, plethora of pathogens harboured, and efficient vector competence in spreading multiple pathogens suggests profound role ofStomoxyson pathogen transmission and infection prevalence in livestock.

Author summary

Stomoxysflies are highly adaptable to several ecological settings, including metropolitan areas. In contrast, tsetse flies (genusGlossina), the main biological vectors of African trypanosomes, have a limited distribution to parks and other conservation areas.Stomoxysflies could play a significant role in the spread of animal African trypanosomes, among other hemopathogens, particularly in areas with or without tsetse infestation. Although there have been speculations about the potential role ofStomoxysflies in the transmission of various pathogens, there is lack of data to link hemopathogens occurring in both bloodmeal hosts ofStomoxysand in the flies, and furtherin vivoexperimental studies to confirm the vector competence of Stomoxyine flies. Here, we explored a host and pathogens network, and investigated species diversity at various ecologies, and demonstrated thatStomoxysflies feed on diverse vertebrate hosts and are infected with a plethora of pathogens. We also showed experimentally that they could transmit some of these hemopathogens to mice, for instance,T. vivax, T. evansi, Theileria mutans,andAnaplasmaspp. with varying infection success rates.Stomoxysflies could play a significant role in transmitting and spreading various hemopathogens of veterinary importance and possibly maintaining their circulation in livestock, which could explain the occurrence of animal African trypanosomes in the regions outside the tsetse belts.