World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of ectoparasiticides against biting and nuisance flies on ruminants

Epidemiological and therapeutic studies on sheep lice in Sayint district, South Wollo Zone, Northeast Ethiopia

An epidemiological (cross-sectional) and therapeutic (randomized controlled field trial) study was conducted on sheep lice in Sayint district, South Wollo, Northeast Ethiopia. The aim of the study was to (i) quantify the magnitude of sheep lice burden and the prevailing lice species, (ii) identify and quantify risk factors affecting lice infestation in sheep, and (iii) evaluate the efficacy of commonly used acaricides (diazinon and ivermectin) against sheep lice infestation. A total of 232 randomly selected sheep, 15 naturally infested sheep, and 80 viable Bovicola ovis lice were used for epidemiological, in vivo, and in vitro based therapeutic studies, respectively. Three naturally infested treatment groups each with five sheep (Group I—treated with diazinon, Group II—treated with ivermectin, and Group III—untreated/control) were used for in vivo therapeutic study. Lice count for the corresponding treatment groups was conducted on weekly basis using clinical and parasitological examinations. We used logistic regression to quantify the association between different putative risk factors and lice infestation, and the independent t-test and one-way ANOVA to compare the within and between treatment group mean lice count variations. The overall prevalence of sheep lice in the study area was 48.3%, where Bovicola ovis (83%) was the dominant lice species. Hair length, body condition, agroecology, and season were significantly (P < 0.05) associated with sheep lice infestation. Analysis of variance revealed that mean lice count significantly (P < 0.05) varies between treatment groups. A significant (P < 0.05) low mean lice cunt was recorded in diazinon- and ivermectin-treated groups when compared to untreated group. The in vivo efficacy of ivermectin (81%) was lower than diazinon (99%) when compared to the efficacy standard limit (98–100%). However, no significant mean lice count variation was recorded between the two groups. In vivo (99%) and in vitro (95%) assay evidence revealed that diazinon was highly effective for the treatment of sheep lice. According to this study, it can be concluded that the magnitude of sheep lice burden in Sayint district was found to be high and this could have a potential negative impact on sheep productivity and health performances. Thus, applying an appropriate intervention measure including the right choice of effective acaricides could help to control sheep lice in the study area.

General Considerations for On-Animal Ectoparasiticidal Product Evaluations

Successfully preparing for and conducting on-animal ectoparasiticidal evaluations is key in providing accurate results and inferences on product performance. However, the procedures associated with designing sound-reliable research projects while using animal test subjects can become complex. The current manuscript offers insights towards the characterization of different evaluation types highlighting key considerations and potential problematic barriers that may otherwise be overlooked by researchers new to the area of on-animal product evaluation. Furthermore, recommendations on reporting inferences from findings based on various study designs are discussed. The authors of the current manuscript offer these considerations in the hopes of maintaining harmony in future reports used to develop and evaluate on-animal ectoparsiticidal products in the field of veterinary entomology.

Fitness cost, realized heritability and stability of resistance to spiromesifen in house fly, Musca domestica L. (Diptera: Muscidae)

The house fly, Musca domestica L. (Diptera: Muscidae), is an insect pest of public health and veterinary importance. Spiromesifen is a new chemistry insecticide widely used for the management of sucking insect pests of vegetables and crops. In the present study, assessment of resistance risk and fitness costs associated with spiromesifen resistance in M. domestica was studied. Moreover, stability of resistance to spiromesifen and other tested insecticides (fipronil, spinosad, and bifenthrin) was evaluated in the spiromesifen-selected-strain (SPIRO-SEL-POP). After 7-generations of selection with spiromesifen, SPIRO-SEL-POP developed 108.76-fold resistance compared with the unselected strain (UNSEL-POP). The estimated value of realized heritability was 0.59 for spiromesifen resistance. Due to withdrawal of spiromesifen selection for five generations (F₆-F₁₀) on SPIRO-SEL-POP, a decline in LC₅₀ values against spiromesifen, spinosad and bifenthrin was 0.16, 0.14 and 0.13-folds, respectively. In biological trait experiments, larval weight of Cross₁ (SPIRO-SEL-POP♀ × UNSEL-POP♂) and SPIRO-SEL-POP was significantly lower than that of Cross₂ (SPIRO-SEL-POP♂ × UNSEL-POP♀) and UNSEL-POP. Pupal weight of SPIRO-SEL-POP was higher when compared with Cross₁ while it was similar to that of Cross₂ and UNSEL-POP. Adult emergence rate of UNSEL-POP was higher than Cross₁, but similar to the Cross₂ and SPIRO-SEL-POP. The SPIRO-SEL-POP and Cross₁ showed the lowest relative fitness when compared with USEL-POP and Cross₂. Intrinsic rate of natural increase of SPIRO-SEL-POP was much lower than that of UNSEL-POP and Cross₂ followed by Cross₁. The SPIRO-SEL-POP exhibited lower biotic potential when compared with UNSEL-POP and Cross₂ but similar to Cross₁. Fecundity and hatching rates were lower in SPIRO-SEL-POP compared to UNSEL-POP. It could be concluded that spiromesifen resistance in M. domestica comes with a cost and is instable. Therefore, spiromesifen rotation with other insecticides and withdraw of its usage for some period could help to sustain its efficacy by delaying the development of resistance.

In vitro test for the evaluation of the efficacy of topical products for the control of Cochliomyia hominivorax larvae

Cochliomyia hominivorax larvae cause myiasis in animals and humans. To register a commercial product to control this dipteran is necessary to experiment on animals. The in vitro test was standardized to evaluate the larvicidal efficacy of commercial topical products. Five formulations were analysed in vitro and in vivo. For the in vitro test, a colony was formed and three replicates (n = 200) of each larval stage (L1, L2 and L3) were treated. The viability of the larvae was evaluated after 5 and 30 min, and at 1, 2, 6, 12, 24, 48, 60 and 72 h post-treatment (HPT). For the in vivo test, 30 bovines divided into six groups were castrated to achieve natural infestation with C. hominivorax. Animals in the treated groups received the product. Myiasis and efficacy were evaluated 12, 24, 36, 48, 60 and 72 HPT. Four formulations tested in the in vitro test achieved 100% efficacy at 24 HPT. In the in vivo experiment only one achieved 100% efficacy at 24 HPT. However, all products achieved the maximum efficacy by the end of study. The in vitro test developed here could be adopted to evaluate the efficacy of topical products for the control of C. hominivorax larvae.

Eficácia do diflubenzuron 25% no controle da Haematobia irritans (Diptera: Muscidae): desafio in vitro e a campo

Avaliou-se, neste experimento, a eficácia in vitro e in vivo do diflubenzuron a 25% para uso em bovinos, no controle da infestação por Haematobia irritans. Para o teste in vitro, ovos de moscas-dos-chifres foram mantidos em recipientes contendo fezes de animais não-tratados ou tratados com diflubenzuron a 25%, e acompanhados até emergência dos adultos. No teste in vivo, foram utilizadas 40 fêmeas aneloradas, divididas em dois grupos: controle (C) e tratado (T) com intensidade parasitária equivalente. Durante o experimento, o grupo C recebeu apenas suplementação mineral, enquanto o grupo T recebeu suplementação mineral e diflubenzuron a 25%. A contagem de moscas nos animais foi realizada na região dorsal, desde a nuca até as pontas da anca de cada animal, no início e ao final de um período de cinco meses. Na avaliação in vitro, o grupo controle apresentou média de emergência de 86% (± 8,4%), enquanto o grupo cultivado em fezes de bovinos tratados com diflubenzuron a 25% apresentou taxa de emergência média de 1% (± 0,2%), sendo a eficácia calculada de 98,83%. No teste in vivo, não foi observada redução significativa na contagem de moscas no grupo C, porém, no grupo T houve significativa redução da infestação por H. irritans (t = 16,46, p < 0,0001). A eficácia do produto, em condições de campo, foi de 99,20%. O diflubenzuron a 25% adicionado ao sal mineral mostrou-se eficaz contra H. irritans, sendo indicado para esse fim.

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of parasiticides for the treatment, prevention and control of flea and tick infestation on dogs and cats

These guidelines are intended to assist the planning and conduct of laboratory and clinical studies to assess the efficacy of ectoparasiticides applied to dogs or cats for the purpose of treating, preventing and controlling flea and tick infestations. The term ectoparasiticide includes insecticidal and acaricidal compounds, as well as insect growth regulators. The range of biological activities accruing from animal treatment that are considered include: repellency and anti-feeding effects, knockdown, speed of kill, immediate and persistent lethal effects, and interference with egg fertility and subsequent development of off-host life cycle stages. Information is provided on the selection of animals, dose determination, dose confirmation and field studies, record keeping, interpretation of results and animal welfare. These guidelines are also intended to assist registration authorities involved in the approval and registration of new parasiticides, and to facilitate the worldwide adoption of harmonized procedures.