Seasonal variations in the larval burden distribution of Oestrus ovis in sheep in the southwest of Spain

A chronobiological study of oestrosis was conducted for larval instars of Oestrus ovis from November 2000 to September 2002 with the examination of 477 adult sheep of the southwest region of Spain. Skulls from slaughtered sheep were examined and the different O. ovis larval stages (L1, L2, L3) were recovered from the nasal-sinus cavities. O. ovis larvae were detected in 339 sheep, reaching a prevalence of 71.1%. Only one farm was free of infested sheep indicating a prevalence of the 97.91% among studied flocks. The mean larval burden was 18.54 larvae per infested head during the coldest months in the southwest of Spain when the larval burden reached its highest levels, especially of the first larval stage (L1). However, the maximum percentage of L1 coincided with the minimum percentage of the second larval stage (L2). The third larval stage (L3) was observed in relatively low levels during the entered study period, but two peaks occurred in April-May and in September-October. During the 2 years of sampling, all the different larval stages were simultaneously recovered throughout the year, indicating the existence of a long favourable period for the evolution and development of the larval instars, which would start between February and March and finishing in November.     

Oestrus ovis myiasis in Libyan sheep and goats

Summary The heads of 1,489 sheep and 320 goats were examined for larvae ofOestrus ovis at 17 abattoirs in northern Libya in July to November 1988. The prevalence ofO. ovis in sheep was 22·6% and in goats it was 18·4 per cent. Up to 14 and 11 larvae were collected from individual sheep and goats respectively. All larvae were recovered from the nasal passages and frontal sinuses, but only second and third instars were seen.

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Miasis Causada PorOestrus Ovis En Ovejas Y Cabras Libias

Resumen Durante los meses de julio a noviembre de 1988, se examinaron las cabezas de 1489 ovejas y 320 cabras para detectar larvas deOestrus ovis, en 17 mataderos en el norte de Libia. La prevalencia deO. ovis en ovejas fue de 22·6% y en cabras de 18·4%. Se localizó hasta un máximo de 14 y 11 larvas en cabezas ovinas y caprinas respectivamente. Todas las larvas fueron recuperadas de las fosas nasales y los senos frontales; sólo se encontraron los estadíos larvarios segundo y tercero.

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Myiase A Oestrus Ovis Chez Des Ovins Et Caprins En Libye

Résumé Les têtes de 1 489 moutons et de 320 chèvres ont été examinées dans 17 abattoirs de la Libye du nord, de juillet à novembre 1988, pour rechercher des larves d'Oestrus ovis.La prévalence d'Oestrus ovis chez les moutons était de 22,6 p. 100 et chez les chèvres de 18,4 p. 100. Le nombre maximal de larves trouvées par animal a été de 14 chez les moutons et 11 chez les chèvres. Toutes les larves ont été récoltées des conduits nasaux et des sinus frontaux, mais seuls les deuxièmes et troisièmes stades ont été observés.

     

Oestrus ovis larval myiasis among goats in northern Jordan

From December 1998 to December 1999, heads of 520 local goats slaughtered at the Irbid, Ramtha and Howarra Abattoirs (northern Jordan) were examined for the three larval instars (L(1)-L(3)) of Oestrus ovis. Of 520 heads, 126 (24%) were infested with O. ovis larvae. All three larval instars were observed in both sexes; all age groups were infested in each month of the year. The mean age of the goats sampled was 1.5 years. The numbers of parasites infesting hosts showed a significant (P<0.05) correlation with sheep age (r(sp)=0.31-0.42) for all three larval instars. The numbers of larvae in each host followed an overdispersed distribution, which fit a negative-binomial model (but not a Poisson distribution). There were more parasites recorded in the presence of purulent discharge or laryngitis, fewer in the presence of catarrhal discharge and no association with pharyngitis sinusitis, or rhinitis.     

Seroprevalence of Oestrus ovis infection in sheep in southwestern Germany

The aim of the survey was to determine the seroprevalence of Oestrus ovis infection in flocks in southwestern Germany. Serum samples collected from 1497 sheep (>6 months of age) of 110 flocks in 1997 and 1998 were examined for antibodies to crude somatic antigens of O. ovis second-stage larvae using an ELISA test. Data on the farm management were obtained by a questionnaire. Overall, 76% of the flocks had at least one seropositive animal, and the seroprevalence of anti-Oestrus antibodies was 50% in sheep. Flock size was the only risk factor significantly associated with the detection of antibodies. Larger flocks (>50 ewes) were more likely to be seropositive than smaller ones. These results show that Oestrus infections are widespread in sheep in southwestern Germany. Further investigations are required to estimate the economic importance of oestrosis and the efficiency of control measures.     

Epidemiology of Oestrus ovis infection of sheep in the highveld of Zimbabwe

During a period of 13 months, 507 heads of sheep, obtained from an abattoir near Harare, were examined for infection with Oestrus ovis larvae. The prevalence of infection varied from 6 to 52%, the highest being in November and the lowest in April. The mean annual larval burden was 1.12. The maximum number of larvae recovered from a single head was 57 in the month of November. Two larval peaks were observed, the first and highest in November and the second in August/September. Some flies are present throughout the year, except in May. There are at least 3 generations of flies per year. The wet summer period from January to May seems to be unfavourable, as very few flies are present. There is no overwintering of first instar larvae in the heads of sheep.     

Genetic structure of Oestrus ovis populations in sheep and goats.

A genetic analysis using RAPD markers was performed on 12 natural populations of Oestrus ovis (Linné, 1761). Three-hundred and six O. ovis larvae (first, second and third instars) were randomly recovered in nasal cavities of sheep and goats naturally infected in Algeria, Ethiopia, France, Mauritania, Rumania and Tunisia and were analysed by 56 RAPD fragments. The results showed a high diversity within all samples. A significant genetic divergence was showed by discriminant analyses among the 12 populations sampled (p<0.0001). Moreover, discriminant analyses showed significant differentiation (p<0.0001) between O. ovis larva populations of sheep and goats and also among samples collected in the same region.     

Persistent efficacy of a long acting injectable formulation of moxidectin against natural infestations of the sheep nasal bot (Oestrus ovis) in Spain

Cydectin(?) 2% LA Solution for Injection for Sheep (Pfizer Animal Health) is a long-acting (LA) formulation of moxidectin for the treatment and prevention of mixed infections of gastro-intestinal nematodes, respiratory nematodes and certain arthropod parasites in sheep. To evaluate the duration of persistent efficacy against nasal bots (Oestrus ovis), a natural exposure study was conducted in Spain during the summer of 2011. One hundred and twenty nasal bot-free, Rasa Aragonesa sheep were randomly allocated to eight groups of 15 animals each. On Day 0, four groups were treated at the recommended dose rate of 1 mg moxidectin/kg bodyweight. Four groups remained untreated as negative controls. All animals were held in nasal bot-proof housing except for exposure to natural challenge when one group of treated sheep and one of group of control animals were transferred to a local pasture at either 0-20, 20-40, 40-60, or 60-80 days after treatment. Following challenge, sheep were scored for clinical signs of bot infestation, necropsied and the heads sectioned for larval recovery. Nasal bot larvae were retrieved from 7 to 11 control sheep following each exposure period indicating that adult bots were active throughout the study. In the first challenge up to 20 days after treatment, when sheep were slaughtered immediately after exposure, the majority of larvae were first instar (L1) and only 3 of the 15 control sheep were infested with second instars (L2). There was 100% efficacy against L2 and 38.1% reduction in the number of live L1 in the treated sheep but mean counts were not significantly different between treatment and control groups (P ≥ 0.05). For the subsequent exposure periods 20-80 days after treatment (necropsies 7-9 days after challenge), 6-10 sheep were infested with L1 and 9-11 control sheep were infested with L2 and third instars (L3). There was negligible efficacy against L1, but treatment with moxidectin resulted in 100% control of L2 and L3. These results are consistent with the biology of nasal bots and control with a systemic agent, as the slower growing L1 have limited feeding and are therefore less susceptible to systemic parasiticides. The study demonstrated that the persistent efficacy of this long-acting injectable formulation of moxidectin protects against the development of active O. ovis infestations for at least 80 days after treatment.     

Efficacy of eprinomectin pour-on against gastrointestinal nematodes and the nasal bot fly (Oestrus ovis) in sheep

The efficacy of the pour-on formulation of eprinomectin, at a dose rate of 0.5 mg/kg bodyweight, was assessed in sheep against three main species of gastrointestinal nematodes and against the nasal bot fly, Oestrus ovis, and some pharmacokinetic parameters were determined for 21 days after the treatment. By comparison with untreated control sheep, infected experimentally with Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis, eprinomectin was 100 per cent effective against the two abomasal species and 99.5 per cent effective against T. colubriformis. In ewes naturally infected with the nasal bot fly, the efficacy of the drug against O. ovis was 97.7 per cent. The mean (se) systemic area under the curve (AUC) was 56.0 (26.2) ng/day/ml and the mean residence time was 5.3 (1.0) days, but there were wide variations between individual sheep.     

Parasitism by Oestrus ovis: influence of sheep breed and nematode infections

Previous studies showed that Santa Ines (SI) hair sheep were more resistant to gastrointestinal nematode infections (GIN) than Ile de France (IF) sheep. The present experiment aimed to evaluate if that reported resistance difference against GIN also occurred against Oestrus ovis infestation and also to evaluate the influence of O. ovis infestation on the gastrointestinal nematodes (GIN) infections. SI (n=12) and IF (n=12) young male lambs were weaned at 2 months of age and moved to a paddock (0.3 ha) with Brachiaria decumbens grass, where they also received concentrate ration. The animals were kept together during the experimental period (September to early December 2009). Fecal and blood samples were taken from all animals every 2 weeks and body weight and nasal discharge score (oestrosis clinic signs) were recorded on the same occasion. In early December 2009, all lambs were sacrificed and O. ovis larvae and GIN were recovered, counted and identified according to the larval stage. All animals were infested by different larval instars of O. ovis without any statistical difference between breeds (P>0.05). The SI lambs had an average of 24.8 larvae, and the intensity of infection ranged between 14 and 39 larvae, while the IF lambs showed an average of 23.5 larvae with the minimum and maximum from 11 to 36 larvae, respectively. SI lambs presented the lowest nematode fecal egg counts (FECs) and the lowest mean numbers of Haemonchus contortus, Trichostrongylus colubriformis and Strongyloides papillosus, however, there was no significant differences between group means (P>0.05). Inverse relationship between numbers of O. ovis larvae and gastrointestinal nematodes was observed in both breeds. SI sheep showed a significant increase in blood eosinophils and total IgE serum levels and these variables were negatively correlated with nematode FEC. A negative correlation was observed between total IgE serum level and H. contortus burden in both breeds. In conclusion, there was no breed difference regarding O. ovis infestation and in each breed, animals with more nasal bot fly larvae tended to display smaller worm burden.     

Vaccination against Brucella ovis infection in sheep

Extract

Dairy cows in New Zealand subsist chiefly on pasture or pasture products such as hay and silage, whilst concentrates are fed only in exceptional cases. Town supply herds are concerned with the production of winter milk and payment by the dairy factory is based on their milk production assessment during the months of June, July, and August. It is therefore necessary to have maximum milk production during these winter months when pastures are at their minimum rate of growth. As a food supplement, therefore, many town supply herds augment their feeding with crops and wet brewers' grains. The grains are fed from hoppers in the bail and are also spread out in the paddocks or placed in large wooden troughs. Most grains are purchased on a contract basis from the brewers, more being available during the summer months, when more beer is consumed. Friday's load of grains is usually stored and the consumption spread out over the week-end until the first fresh load is brought in on Monday morning.     

Evaluation of a direct ELISA for the serodiagnosis of Oestrus ovis infections in sheep.

Oestrosis is a parasitic disease of sheep and goats caused by the nasal bot fly Oestrus ovis. In the United Kingdom the economic losses as a result of infestation can be considered negligible, but the differentiation of O ovis cases from more serious diseases such as listeriosis, gid and sheep scab is of considerable importance. Currently, diagnosis of oestrosis relies on the subjective observation of clinical signs or the demonstration of larvae postmortem. This paper assesses the effectiveness of a direct enzyme-linked immunosorbent assay (ELISA) using a crude somatic antigen from first-stage larvae (L1) in the serodiagnosis of oestrosis. The system has been validated with sera from both endemic and non-endemic areas and the results correlated with the clinical data found postmortem. The sensitivity and specificity of the assay were 97.4 per cent and 97.6 per cent, respectively, using a cut-off point based on 35 per cent binding of a reference positive control serum.     

Expected effects of reducing Oestrus ovis L. mature larval weight on adult populations

In order to estimate the effects of eventual reductions in larval weight (LW) of Oestrus ovis L. as a measure of control, the correlation between mature LW and adult fly length (AL) in laboratory specimens (n=150) was calculated. The regression equation AL=5.62+10.65LW (r(2)=0.76) was obtained. This equation was then applied to estimate the mature LW of wild larvipositing females (n=51) to predict the minimum mature LW at which fly viability would be compromised. The critical weight, 0.28 g (standard error limits 0. 235, 0.323), was obtained from a small fly measuring 8.6mm in length. Data from 383 mature third instars were used to estimate, by statistical analysis, the expected effects of decreasing the mature LW on subsequent fly population size. A considerable mean reduction (38%) in adult populations might be achieved by a 40% reduction of mature LW, but this eventual reduction may be temporary due to the high reproductive rate in this species. Sex differences in mature LW and fly size are also reported.     

Age and seasonal variations in the prevalence of Oestrus ovis larvae among sheep in northern Jordan

During the period March 1996-July 1997, 417 heads of Awassi sheep slaughtered at the Irbid Abattoir (northern Jordan) were examined for the three larval instars (L1, L2 and L3) of Oestrus ovis. Of the 417 heads, 242 (58%) were infested with O. ovis larvae. Larval numbers were highly aggregated. The lowest number of larvae and the lower quartile were both zero, whilst the median was two and the upper quartile was 12. The highest number of larvae recovered from one head was 151. All three larval instars were observed in each month of the year. July and October had the highest proportions of L1, 75 and 78%, respectively, among infected animals (adjusted for age). The number of larvae increased with age. Infestation with live larvae was associated with inflammatory responses in the upper respiratory tract and with catarrhal or purulent discharge. The percentage of infested sheep and the mean monthly total number of larvae/sheep peaked in the warmer part of the year. Most larvae were L1 except during the spring when L2 and L3 predominated. Distribution analysis demonstrates that the numbers of larvae recovered in the sheep population followed a negative-binomial distribution. Furthermore, the negative-binomial constant k for each month correlated with the monthly prevalence.     

Comparison of infection rates of Oestrus ovis between sheep and goats kept in mixed flocks

Oestrosis is a nasal myiasis of sheep and goats caused by larvae of the fly Oestrus ovis and can lead to severe clinical signs, which together with the disturbance caused by the adult fly may result into serious economic losses. Infection rates and larval burdens are always higher in sheep than in goats after either natural or artificial infestation. The aim of this study was to compare the host preference of the adult fly O. ovis between sheep and goats in mixed flocks, where they are kept together under the same husbandry conditions and hence, are very similarly exposed to the fly preference. Blood sera samples were collected from a total of 397 sheep and 335 goats, from 43 mixed flocks located at different regions of Greece. Antibodies specific to O. ovis IgG were measured by ELISA. A flock was considered positive when at least one individual was positive, i.e. showed a seropositivity of >or=20% in relation to positive control sera. A total of 193 (48.6%) sheep and 58 (17.9%) goats were found to be seropositive against O. ovis. Thirty-eight (88.4%) out of 43 flocks had at least one seropositive animal. The mean seroconversion against O. ovis in animals from the different flocks was 38.6% and 13.6% for sheep and goats, respectively, whereas the variance of infection within each flock was 0-100%. The mean seropositivity between sheep that were found to be positive or negative was 60.6% and 5.4%, respectively, whereas the corresponding values between goats were 35.2% and 5.2%, respectively. No significant difference in the seroconversion values was noted between flocks from the different areas (P=0.817), whereas a very significant difference was observed between animal species (P=0.001). However, there was no significant difference when seroconversion comparisons were made within samples of the same animals species, sheep or goats from different flocks of all the regions included in the study (P=0.695). The results of this study clearly demonstrate that O. ovis has a widespread distribution in Greece, and the seroprevalence is significantly higher in sheep than goats (P=0.001).     

Proteolytic activity in salivary gland products of sheep bot fly (Oestrus ovis) larvae

This study identified and characterized hydrolytic enzymes in salivary gland products of Oestrus ovis larvae. Third instars were collected from the heads of slaughtered goats. Salivary glands were extracted, their products obtained by centrifugation and the enzymatic profile determined. Optimum pH, temperature of maximum proteolytic activity, thermal stability, and resistance of salivary gland products were determined on collagen and subclasses of proteases were identified using protease inhibitors. Zymograms were used to determine the molecular weight of proteases. Antigenic protein bands were revealed by immunoblotting using sera obtained from experimentally infested goats. Seven positive enzymatic activities were detected in salivary gland products: acid phosphatase, naphthol-AS-BI-phosphohydrolase, esterase (C4), esterase lipase (C8), leucine arylamidase, alpha-glucosidase and N-acetyl-beta-glucosaminidase. Optimum pH for proteolytic activity was 8.0; proteolytic activity increased with temperature (10-50 degrees C) then drastically decreased at 60 degrees C. Proteases in O. ovis salivary gland products belong to the serine subclass. In Zymograms, bands of proteolytic activity were detected in the 20-63 kDa range; the immunoblot showed three antigenic bands, one of them related to a protease band (63 kDa). Serine proteases in O. ovis salivary gland products are most likely involved in larval nutrition and host immuno-modulation.     

Oestrus ovis infestation of a dog in the UK

In March 2011, a dog on a sheep farm in the Cotswolds, UK, expelled a mature live third-stage larva of the sheep nasal botfly, Oestrus ovis, after a violent and traumatic sneezing episode. The dog had been infected with first-stage larvae deposited by an adult fly the previous autumn; larval development had progressed throughout the winter and spring with few apparent clinical signs and possibly masked by ongoing immunotherapy for an unrelated condition. Identification of the parasite at the Liverpool School of Veterinary Science was made from a submitted puparium, the "chrysalis" stage to which the larva had progressed within days of its expulsion from dog's nose. To the authors' knowledge this is the first report of nasal botfly infestation of a dog in the UK.     

Parasites of domestic and wild animals in South Africa. I. Oestrus ovis in sheep

Separate groups of 3 oestrid-free lambs were exposed to infestation on irrigated pasture for periods of approximalely 33 days each over30 months, and on dry-land pasture for approxomately 42 days over a period of 18 months. With some exceptions, the lambs slaughtered from October-June were found to be infested with Oestrus ovis while, with one exception, those slaughtered from July-September were free. A minimum of 4 sheeps' heads, obtained weekly over 24 months from the Pretoria Municipal Abattoir, was examined for infestation. Of a total of 542 heads examined, 73,4% were infested, having a mean burden of 15,2 larvae. Mean larval burdens were slightly greater in hornless than in horned sheep in Dorper-type than in Merino-type sheep, and in lambs than in sheep with 2 or more permanent incisors. The largest larval burdens were recovered from sheep slaughtered during May and June and the smallest during September and October. The greatest number of 1st instar larvae were recovered during May and June and the smallest during September, but those recovered during the latter month were the largest. With one exception, mature larvae which pupated after 21 March or before 16 August failed to hatch as viable flies. Those which pupated after 16 August hatched as flies after a pupal stage of approximately 50 days and the first flies to hatch were invariably recovered during the first 2 weeks of October. The pupal stage decreased to approximately 25 days during December and January and increased again to approximately 50 days for flies hatching during May. No flies hatched between 18 May and 1 Cctober. The following life cycle ofr Oestrus ovis is suggested: sheep are repeatedly infested from October-June; thereafter infestation survives in the sheeps' heads until August, mainly as 1st instar larvae, then as pupae and larvae until fresh infestation takes place during October.