Efficacy of lotilaner against myiasis caused by Cochliomyia hominivorax (Diptera: Calliphoridae) in naturally infested dogs.

BACKGROUND: The New World screwworm fly, Cochliomyia hominivorax, is widely distributed across South America. This parasitic insect is a significant cause of primary myiasis in animals, including dogs. There is an urgent need for a rapid and efficient treatment to improve the recovery of affected animals. In the present study we evaluated the potential of lotilaner for the treatment of myiasis caused by C. hominivorax larvae in naturally infested dogs. Lotilaner belongs to the isoxazoline class of chemical compounds and is marketed as Credelio™ for use against ticks and fleas in dogs and cats. METHODS: Eleven dogs with naturally acquired myiasis were enrolled in this study based on the severity of lesions and the number of identified larvae. All animals received a single oral administration of lotilaner at a minimum dose of 20.5 mg/kg body weight. After treatment, the number of expelled larvae, live or dead, was determined at 2, 6 and 24 h, and the larval expulsion rate, larvicidal effect and overall efficacy were calculated. After 24 h, the remaining larvae were removed, counted and identified. The lesions were cleaned, and palliative treatment was administered when necessary, according to the animal's health status. RESULTS: All larvae were identified as C. hominivorax. The larval expulsion rate was 80.5% and 93.0% at 2 and 6 h post-treatment, respectively. Lotilaner showed an overall efficacy of 100% at 24 h post-treatment. CONCLUSIONS: Lotilaner demonstrated a rapid onset of action and a high efficacy against C. hominivorax. We therefore recommend lotilaner for the effective treatment of myiasis in dogs.

Occurrence and anatomical distribution of myiasis caused by Cochliomyia hominivorax (Diptera: Calliphoridae) in swine.

Cochliomyia hominivorax (Diptera: Calliphoridae) has been considered the most important cause of myiasis in animals in the South America with most cases being recorded in cattle. In Brazil, the risk of myiasis in swine population is underestimated, leading to difficulties in the implementation of preventive measures. The aim of this study was to report the occurrence of myiasis infesting a swine population over a one-year period and to evaluate the anatomical distribution of these larvae on the animal's body. From May 2019 to April 2020, a total of 2038 inspections were carried out on pigs reared in two farms located in the state of Pernambuco, Northeastern Brazil. Fly larvae retrieved were morphologically identified and the anatomical distribution of myiasis was graphically represented by a heat map indicating its frequency in swine based on the interpolation of data. Cochliomyia hominivorax larvae (n = 78) of second (n = 29) and third (n = 49) developmental stages were recovered in 13 animals (0.64%) out of 2038 inspections performed. The occurrence of myiasis was detected in eight anatomical sites, with higher concentration on the forehead region and on ears. Data herein obtained provide valuable information on the epidemiology and biological aspects of C. hominivorax affecting pigs. In addition, it indicates that the forehead and ears are important sites of parasitism most likely due the high frequency of skin lesions in these areas.

Efficacy of sarolaner on the treatment of myiasis caused by Cochliomyia hominivorax (Diptera: Calliphoridae) in dogs.

The aim of this study was to evaluate the larval expulsion, larvicidal effect, retention rate of dead larvae and overall efficacy of sarolaner on the treatment of myiasis caused by New World screwworm Cochliomyia hominivorax in naturally infested dogs. Eight Beagle dogs received a single dose of saroalner 40 mg, with dosage ranging from 2.7 mg/kg to 3.7 mg/kg. Evaluations occurred every 15 min in the first hour, every hour for up to 6 h, and after 24 h of treatment. At 24 h post-treatment, total wound cleaning was performed, including removal and counting of remaining live and dead larvae. The animals received antibiotic, analgesic and wound cleaning support until complete wound healing. The average expulsion of the larvae was 50.9 % occurring mainly after 4 h of treatment. The larvicidal effect was 70.6 % at 6 h after treatment and 100 % at 24 h. The mean retention rate of dead larvae of sarolaner was 33.9 %, The overall efficacy was 100 %, thus making sarolaner an excellent treatment option in myiasis caused by C. hominivorax larvae in dogs.

Epidemiological analysis of the New World screwworm (Cochliomyia hominivorax) in Ecuador.

The New World screwworm (Cochliomyia hominivorax) is an obligate parasite that affects warm-blooded animals. It causes myiasis in livestock and humans, which is a problem for animal production and public health. The health and economic burden of myiasis on livestock production is largely unknown in Ecuador. We investigated the presence of the screwworm and analysed the epidemiology and spatial and temporal trends of myiasis in cattle farms of San Miguel de Los Bancos county. In total, epidemiological questionnaires were conducted in 110 farms, which were subsequently monitored for 12 months. The findings show that the initial and final prevalences in farms were 70% and 61.81%, respectively, and the average monthly prevalence was 15.08%. The initial and final prevalences in animals were 3.87% and 4.60% for bovines and 2.91% and 3.36% for all animals examined. The average percentage of new cases reported per month was 17.68% with a minimum of 10 and a maximum of 28 cases in October and May 2015, respectively. The cumulative incidence estimated that the risk for non-infested farms to become infested could reach 100% in approximately 6 months. The incidence rate is 168 per 1,000 farms at risk-monthly. The annual incidence was 459 per 10,000 for bovines at risk-annually. An analysis of hotspots based on the Getis-Ord Gi* index revealed no temporally stable hot spot, but one temporally stable cold spot, suggesting that most of the study area is generally favourable to infestation, except one cluster of farms.

Ocorrência de miíases em animais de companhia no Distrito Federal, brasilimação cardiopulmonar / cerebral (RCPC) em cães / Occurrence of myiasis in pets from the Federal District, in Brazil

Background: Myiasis is one of the main causes of infestation by Diptera larvae in animals and human beings. This parasitic disease is frequently diagnosed at veterinary and medical practices. It is classified according to its anatomical location in the host or to its dependency relations and parasitic occurrence. In Brazil, the two diptera species with the highest myiasis incidence in domestic animals are Cochliomyia hominivorax (Calliphoridae) and Dermatobia hominis (Oestridae). These ectoparasites are primarily found in dogs and secondarily in cats, and they are often associated with omission or mistreatment by the owner. This study describes myiasis cases and the main predisposing factors in domestic animals that occurred in 2009 in the Federal District, Brazil. Materials, Methods & Results: Between January and December 2009, veterinary practitioners from 90 small animal practices were requested to supply the larvae collected from clinical myiasis cases. The larvae were kept alive inside biological containers containing vermiculite to preserve their integrity during transportation. Data on the collection month, age, gender, breed, color and type of coat, as well as lesion site, myiasis type and dwelling type were obtained. The larvae were identified in laboratory and then kept inside incubators, fed on rotten bovine meat during 24h. The resulting flies were again identified and sexed. Then the absolute and relative proportions of the clinical cases were obtained, based on the epidemiological factors and respective parasites. Forty cases were recorded (39 of which were dogs and one was a cat). Cochliomyia hominivorax was the most abundant parasite, with 37 cases observed in dogs and only one in a cat. The other two myiasis cases were caused by Lucilia eximia and Musca domestica. In dogs, the highest occurrence of myiasis was observed in males, especially in German Sheepdogs and Cocker Spaniels. The predominant anatomical sites of the disease in dogs were the front limbs and tail. The period in which the disease occurred most frequently was between March and May, period which corresponds to the rainy season in the Brazilian Cerrado. Dogs living in houses within urban areas had the highest parasitism occurrence. Discussion: Myiasis in companion animals is a common finding throughout practices in Brazil and around the world. However, this situation has been under control in North American countries, especially after erradication of myiases caused by C. hominivorax in bovines, which represented great economic losses. Therefore, the incidence of the parasitism in dogs and cats was reduced. In Brazil, obligatory and facultative cutaneous myiases in dogs and cats are caused by omission and mistreatment by the owner. The results presented in this study corroborate the characteristics of neotropical myiases in the Southeast and South region of Brazil in relation to the incidence period and preferential host characteristics, except that the disease has a preference for male light-colored animals, being predominantly observed on the hind limbs. New cases were observed in dogs, particularly in Central Brazil, such as the facultative cutaneous myiasis cases caused by Lucilia eximia and Musca domestica.

Ocorrência de miíases em animais de companhia no Distrito Federal, brasilimação cardiopulmonar / cerebral (RCPC) em cães / Occurrence of myiasis in pets from the Federal District, in Brazil

Background: Myiasis is one of the main causes of infestation by Diptera larvae in animals and human beings. This parasitic disease is frequently diagnosed at veterinary and medical practices. It is classified according to its anatomical location in the host or to its dependency relations and parasitic occurrence. In Brazil, the two diptera species with the highest myiasis incidence in domestic animals are Cochliomyia hominivorax (Calliphoridae) and Dermatobia hominis (Oestridae). These ectoparasites are primarily found in dogs and secondarily in cats, and they are often associated with omission or mistreatment by the owner. This study describes myiasis cases and the main predisposing factors in domestic animals that occurred in 2009 in the Federal District, Brazil. Materials, Methods & Results: Between January and December 2009, veterinary practitioners from 90 small animal practices were requested to supply the larvae collected from clinical myiasis cases. The larvae were kept alive inside biological containers containing vermiculite to preserve their integrity during transportation. Data on the collection month, age, gender, breed, color and type of coat, as well as lesion site, myiasis type and dwelling type were obtained. The larvae were identified in laboratory and then kept inside incubators, fed on rotten bovine meat during 24h. The resulting flies were again identified and sexed. Then the absolute and relative proportions of the clinical cases were obtained, based on the epidemiological factors and respective parasites. Forty cases were recorded (39 of which were dogs and one was a cat). Cochliomyia hominivorax was the most abundant parasite, with 37 cases observed in dogs and only one in a cat. The other two myiasis cases were caused by Lucilia eximia and Musca domestica. In dogs, the highest occurrence of myiasis was observed in males, especially in German Sheepdogs and Cocker Spaniels. The predominant anatomical sites of the disease in dogs were the front limbs and tail. The period in which the disease occurred most frequently was between March and May, period which corresponds to the rainy season in the Brazilian Cerrado. Dogs living in houses within urban areas had the highest parasitism occurrence. Discussion: Myiasis in companion animals is a common finding throughout practices in Brazil and around the world. However, this situation has been under control in North American countries, especially after erradication of myiases caused by C. hominivorax in bovines, which represented great economic losses. Therefore, the incidence of the parasitism in dogs and cats was reduced. In Brazil, obligatory and facultative cutaneous myiases in dogs and cats are caused by omission and mistreatment by the owner. The results presented in this study corroborate the characteristics of neotropical myiases in the Southeast and South region of Brazil in relation to the incidence period and preferential host characteristics, except that the disease has a preference for male light-colored animals, being predominantly observed on the hind limbs. New cases were observed in dogs, particularly in Central Brazil, such as the facultative cutaneous myiasis cases caused by Lucilia eximia and Musca domestica.(AU)