Species Composition and Abundance of Stomoxys spp. (Diptera: Muscidae) in Peninsular Thailand

Biting Flies and Associated Pathogens in Camels in Amibara District of Afar Region, Ethiopia

Biting flies and associated pathogens are the major health constraints on camel production and productivity and are implicated in causing significant economic losses in the pastoralist community in Ethiopia. A cross-sectional study was conducted to estimate the prevalence of biting flies and their associated pathogens in relation to different risk factors in camels in the Amibara district, from October 2019 to April 2020. A total of 480 camels were examined for biting flies and associated pathogens. The study revealed that overall, 87% (418/480) and 18% (87/480) of camels were infested by one or more biting flies and infected with Trypanosoma evansi during the study period, respectively. The collected biting flies were identified into a total of 3 genera: Hippobosca, Stomoxys, and Tabanus under the stereomicroscope. In the present study, Hippobosca (40.4%) was the most prevalent biting fly, followed by Stomoxys (31%) and Tabanus (28.6%), which affected camels in the study area. Among camels infected with Trypanosoma evansi, 7.3% and 16% were positive for parasitological and serological tests, respectively. Age, body condition score, and season appeared to have a significant effect (p ≤ 0.005) on the prevalence of biting flies and T. evansi on dromedaries. According to the findings of this study, biting flies and Trypanosoma evansi were the most common limitations on camel health, production, and productivity in the study area. As a result of the possible threat of biting flies' infestation and Trypanosoma evansi on camels, all-around attention is required in terms of strategic acaricide application, proper antiprotozoal drug use, and raising knowledge about acaricide use to prevent and control biting flies' infestation.

Preliminary study on prevalence of hemoprotozoan parasites harbored by Stomoxys (Diptera: Muscidae) and tabanid flies (Diptera: Tabanidae) in horse farms in Nakhon Si Thammarat province, Southern Thailand

Background and Aim

Stomoxys and tabanid flies are of medical and veterinary importance because they play crucial roles in disease transmission as mechanical vectors of various hemopathogens. However, its role as a hemoprotozoan parasite vector in horse farms has not been studied. Therefore, we investigated the occurrence of hemoprotozoan parasites belonging to the genera Babesia, Theileria, and Trypanosoma in Stomoxys and tabanid flies using conventional polymerase chain reaction (PCR) and DNA sequencing.

Materials and Methods

All samples (Stomoxys and tabanid flies) were collected using an Nzi trap for three consecutive days each month from November 2022 to March 2023. The flies were morphologically identified to the species level and separated according to sex. Individual (for tabanid flies) or pooled samples (consisting of three specimens of Stomoxys flies of the same species and sex collected from the same site) were used for DNA extraction. Conventional PCR was used to screen for hemoprotozoan parasite DNA, followed by Sanger sequencing to identify the species.

Results

In total, 189 biting flies were collected, including four species of Stomoxys (Stomoxys bengalensis, Stomoxys calcitrans, Stomoxys indicus, and Stomoxys sitiens) and five species of tabanids (Atylotus cryptotaxis, Chrysops dispar, Tabanus megalops, Tabanus mesogaeus, and Tabanus rubidus). Stomoxys calcitrans was the most prevalent species, accounting for 58.7% (n = 111) of the collected flies. Ten (12.4%) of the 81 samples (individuals and pools) analyzed by PCR were positive for the 18S rRNA gene of the Theileria/Babesia species. Trypanosoma DNA was not detected in any sample. After performing Basic Local Alignment Search Tool searches and a phylogenetic analysis, only six samples (7.4%), including S. calcitrans (n = 2), S. sitiens (n = 2), T. megalops (n = 1), and A. cryptotaxis (n = 1), were found to be infected with Theileria sinensis. Furthermore, apicomplexan parasites, namely, Mattesia spp. and Colpodella spp., were found on S. indicus, the fungus Meira spp. was found on S. calcitrans, and the pathogenic green alga Helicosporidium spp. was found on A. cryptotaxis.

Conclusion

This study is the first to report a variety of Stomoxys and tabanid flies collected from horse farms in Thailand, which were found to be infected with Theileria and Colpodella species that affect mammals, suggesting that Stomoxys and tabanid flies can be used to confirm the presence of hemoprotozoan parasites in the study area. Understanding the presence of hemoprotozoa in flies could help design vector control programs and manage various diseases in the study area.

Chemical Profiles and Lethal Toxicities of Native Botanical Insecticides for the Control of Musca domestica Linnaeus and Stomoxys indicus Picard (Diptera: Muscidae) in Songkhla Province, Thailand

Livestock farming is currently reducing the use of synthetic insecticides because of the development of resistance in insect pests. Plant-based bioinsecticides are considered alternatives to synthetic pesticides. Therefore, the present study investigated the chemical composition and discriminating concentrations (DCs) of essential oils from Syzygium aromaticum (L.) Merr. and L. M. Perry (SA), Cinnamomum porrectum (Roxb.) Kosterm (CP), and Litsea cubeba (Loureiro) Persoon (LC) against laboratory-reared Musca domestica (larvae and adults) and field-derived Stomoxys indicus (adults) using larval dip and adult contact bioassays. All essential oils were analyzed using gas chromatography/mass spectroscopy. The most common components in the SA, CP, and LC oils were eugenol, safrole, and terpenoids, respectively. The results of a larval test indicated that CP was most effective against M. domestica with a DC of 6.134% v/v. In adult bioassays, CP was also the most toxic oil against M. domestica (DC = 30.644% v/v), whereas SA displayed the greatest toxicity against S. indicus (DC = 1.434% v/v). Moreover, in the larval bioassay results of oils tested at 1, 5, and 10% v/v in M. domestica, 1% and 5% v/v CP had the shortest median lethal times values of 68.88 and 19.44 min, respectively, whereas, at 10% v/v, SA displayed the shortest median lethal time (0.03 min), followed by CP (1.74 min) and LC (19.02 min). However, additional data are needed to further evaluate the semi-field and field effects of CP and SA on M. domestica and S. indicus under realistic operational conditions.

First study on molecular detection of hemopathogens in tabanid flies (Diptera: Tabanidae) and cattle in Southern Thailand

Background and Aim:

Female tabanids play a key role in disease transmission as mechanical vectors for various hemopathogens, but only a limited number of studies have been conducted on them. This study aimed to investigate the occurrence of hemopathogens in tabanid flies compared to those found in nearby cattle hosts.

Materials and Methods:

Tabanids were collected using a Nzi trap for three consecutive days per month during the dry season (February–May 2021). Furthermore, blood samples were collected from 20 beef cattle (Bos taurus) raised in the same area where the flies were captured. Conventional polymerase chain reaction (PCR) was used to detect hemopathogenic DNA in flies and beef cattle.

Results:

In total, 279 female tabanids belonging to five species were collected: Tabanus megalops, Tabanus rubidus, Tabanus mesogaeus, Chrysops dispar, and Chrysops fuscomarginalis. Notably, T. megalops was the most abundant species, accounting for 89.2% of the flies collected (n = 249). PCR technique revealed that 76.6% of T. megalops carried at least one pathogen (Anaplasma, Ehrlichia, Babesia, or Theileria). In addition, all beef cattle had multiple hemopathogenic infections (Anaplasma marginale, Ehrlichia spp., Babesia bigemina, Babesia bovis, and Theileria spp.).

Conclusion:

Although T. megalops could carry many hemopathogens, it might not be an important vector due to the limited number of flies and parasitic load. Furthermore, T. megalops could be utilized to monitor the presence of hemopathogens in the study area, but not the disease occurrence in the individual host species. Knowing the presence of hemopathogens in flies could help manage the disease in this area.

Pyrethroid Susceptibility in Stomoxys calcitrans and Stomoxys indicus (Diptera: Muscidae) Collected from Cattle Farms in Southern Thailand

The susceptibility to six pyrethroid insecticides (permethrin, deltamethrin, alpha-cypermethrin, cypermethrin, lambda-cyhalothrin, and bifenthrin), each at the recommended concentration, was evaluated for two stable fly species-Stomoxys calcitrans (Linnaeus, 1758) and Stomoxys indicus Picard, 1908 (Diptera: Muscidae)-through tarsal contact using a World Health Organization (WHO) cone bioassay procedure. The field populations of S. calcitrans were collected from the Songkhla and Phattalung provinces, while S. indicus were collected from the Phattalung and Satun provinces in Thailand. The stable flies were exposed to insecticide-treated filter paper for 30 min, and their knockdown counts at 30 min and 60 min and mortality counts at 12 h and 24 h were recorded. The S. calcitrans and S. indicus Songkhla and Phattalung populations were moderately susceptible to pyrethroids, as indicated by the 24 h mortality. Nonetheless, the Satun population of S. indicus was completely susceptible to permethrin, with 100% mortality, and showed the lowest susceptibility to deltamethrin and bifenthrin. The results indicate the generally low susceptibility of stable flies to pyrethroids in the southern provinces of Thailand.

Stable fly activity is associated with dairy management practices and seasonal weather conditions

Stable flies (Stomoxys calcitrans) are blood-sucking insects commonly associated with cattle production systems worldwide and are known to cause severe irritation to cattle due to painful bites. Cattle react to biting stable flies with an aggregating behavior known as bunching. Bunching behavior reduces grazing or feed consumption and thus reduces cattle productivity and welfare. Cattle’s fly-repelling behaviors include foot stomping, head tossing, tail switching and skin twitching. A longitudinal study was conducted in 2017 on 20 California dairies (average lactating herd size = 2,466 (SE±28.392)) during the stable fly season from April to July. The study objectives were to estimate the association between environmental factors and dairy characteristics including facility design, feed and manure management, total mixed ration (TMR) components fed to cattle, and operational pest management procedures and the outcome stable fly activity on California dairies. Stable fly activity was measured by counting stable flies on cow forelimbs (leg count) and on Alsynite traps (trap count) over the 13-week study period. Weekly leg counts were performed for cattle in lactating cow pens (31 pens from 10 study dairies) with counts made during the morning (AM) and again during the afternoon (PM). Trap counts were performed on all 20 study dairies. Data were analyzed using linear mixed models which revealed temporal variation in the average leg and trap counts with stable fly activity increasing from May to June and then decreasing to the lowest activity in July. Leg counts were higher during the afternoon compared to morning. Ambient temperatures ≤30⁰C and relative humidity (RH) measurements <50% were associated with higher leg and trap counts. Traps located at the periphery of study dairies had higher stable fly counts compared to traps located in the interior of the dairy. Cow pens with trees on the periphery had higher leg counts in comparison to pens away from trees. Specific TMR components were associated with both leg and trap counts. Dairies feeding by-products including almond hulls, wet distillers’ grain, fruits, and vegetables had higher trap counts compared to dairies that did not feed these ingredients. At the pen level, pens with rations that contained straw had lower average leg counts compared to pens fed with rations that did not contain straw. A similar association was observed for pens with rations that contained wheat silage when ambient temperatures were ≤30⁰C. In contrast, pens with water added to the TMR while the RH was ≥50% had higher average leg counts compared to pens without water added to the TMR. Dairies that applied insecticides for fly control to their entire facility had lower trap counts compared to dairies that did not apply insecticides. Stable fly activity measured on California dairies using leg and trap counts varied according to the month, environmental factors, pen surroundings, trap location, TMR components, and insecticide use.

Methods for Surveying Stable Fly Populations

Stable flies are among the most important pests of livestock throughout much of the world. Their painful bites induce costly behavioral and physiological stress responses and reduce productivity. Stable flies are anthropogenic and their population dynamics vary depending on agricultural and animal husbandry practices. Standardized sampling methods are needed to better identify the factors controlling stable fly populations, test novel control technologies, and determine optimal management strategies. The current study reviewed methods used for a long-term study of stable fly population dynamics in the central Great Plains. An additional study compared the relative size of flies sampled from the general population with that of flies sampled emerging from substrates associated with livestock production. Flies developing in livestock associated substrates are significantly larger than those in the general population indicating that other types of developmental sites are contributing significant numbers of flies to the general population. Because efforts to identify those sites have yet to be successful, we speculate that they may be sites with low densities of developing stable flies, but covering large areas such as croplands and grasslands. The stable fly surveillance methods discussed can be used and further improved for monitoring stable fly populations for research and management programs.