Seasonal variation of Oestrus ovis-specific antibodies in sheep and goats mixed flocks in Greece

Prevalence of Oestrus ovis in small ruminants from the eastern Iberian Peninsula. A long-term study

Oestrus ovis is an obligate parasite that causes myiasis in domestic ruminants, being commonly found in the Mediterranean area. From 2009 to 2019 a total of 3476 heads of culling sheep and goats from the Mediterranean coast of Spain were examined for the presence of O. ovis. The total prevalence was 56.3%, significantly higher in sheep than in goats (61.2% and 43%, respectively). Differences were found in the mean annual prevalence, with the highest value being registered in 2018 (61.7%) and the lowest in 2012 (50.3%). Autumn, for sheep, and winter, for goats, were the seasons with the highest number of infested specimens. Temperature, but not rainfall, was found to be associated with prevalence (p < 0.05). Most L1 were found in the anatomic region I (septum, meatus, and ventral conchae), while L2 and L3 were mainly located in regions II (nasopharynx, ethmoid labyrinth, and dorsal conchae), and III (sinuses). The overall intensity was 12.8 larvae per head, significantly higher in sheep (13.3) than in goats (3.5). Our results confirm the high prevalence of O. ovis in sheep and goats in this geographic area over the last decade, with the trend increasing in recent years in association with higher mean temperatures.

The global and regional prevalence of oestrosis in sheep and goats: a systematic review of articles and meta-analysis

Background

Oestrosis, caused by the larvae of Oestrus ovis, commonly known as sheep nose bot, is an obligatory cavitary myiasis of sheep and goats. Oestrus ovis is a widespread parasite, but little is known about the prevalence of oestrosis at the global and broad geographical levels. The present study aimed to explore the epidemiology of oestrosis at the global and regional level to estimate prevalences and their associated factors using a systematic approach. This is, to the author’s knowledge, the first meta-analysis of oestrosis in sheep and goats.

Methods

Published articles were obtained from nine electronic databases (PubMed, CAB Abstracts, Web of Science, Scopus, UCB library, Medline, Biosis Citation Index, Indian journals and Google Scholar) reporting the prevalence of O. ovis in sheep and goats from 1970 to 2018. Pooled prevalences were estimated using a random effect meta-analysis model.

Results

Sixty-six studies were eligible, and data from 40,870 sheep and 18,216 goats were used for quantitative analysis. The random effect estimated prevalence of oestrosis at the global level in sheep was 51.15% (95% CI: 42.80–59.51%) and in goats was 42.19% (95% CI: 33.43–50.95%). The pooled prevalence estimates for Africa, Asia, Europe and the Americas were 47.85% (95% CI: 36.04–59.66%), 44.48% (95% CI: 33.09–55.87%), 56.83% (95% CI: 48.92–64.74%) and 34.46% (95% CI: 19.90–49.01%), respectively. Heterogeneity (I² > 80%) was detected in most pooled estimates.

Conclusions

Oestrosis is highly prevalent in many geographical regions of the world, especially in Europe and Africa. Factors that contribute to the pooled prevalence estimate of oestrosis need to be emphasised in any survey to estimate the true prevalence of oestrosis. Furthermore, there is a need for immunisation or implementation of other preventive measures to reduce the burden of oestrosis in sheep and goats and to improve the health and welfare status.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3597-2) contains supplementary material, which is available to authorized users.

Oestrus ovis in Ecuador: Importance in the Andean sheep farming

Aim

This study aimed to determine the prevalence of Oestrus ovis in sheep meant for meat commercialization in the main slaughterhouse of the country.

Materials and Methods

Between October 2015 and December 2015, we assessed the occurrence of Oestrus myiasis in the main slaughterhouse localized in Quito. In total, 80 sheep heads were randomly inspected and necropsied. Larvae were removed from nasal cavities and paranasal sinuses and cleaned. ANOVA (generalized linear model) was used to estimate the relationship between sex, age, and place of origin and presence or absence of parasite larvae.

Results

Morphological identification confirmed that 19% (15/80) of the examined animals were positive for Oestrus ovis; from the positive cases, 21% were young animals <12 months old. We found that statistical differences by animal sex, males, were most infested 93% (14/15) than females 7% (1/15). Larvae's L2 were more abundant than other stages (62 of the total 149). 14 of the infested animals were from the Andean places at > 2500 meters above sea level (m.a.s.l.), and only one case from the coastal region at 250 m.a.s.l. with tropical environmental conditions.

Conclusions

Our results showed evidence of the presence of myiasis caused by O. ovis in Andean and coastal places in Ecuador and its adaptation to different environmental conditions from that reported previously in temperate regions from Europe and Africa.

Reliability of an ELISA test for diagnosing oestrosis in Iberian ibex

Oestrosis is one of the most prevalent parasitosis affecting the Iberian ibex, Capra pyrenaica . To date, both the diagnosis of oestrosis and the determination of the intensity of parasitism require the use of invasive methods (necropsy), which necessarily limit research possibilities. We analyzed the immune humoral response (IgM and IgG) against Oestrus ovis L. excretory/secretory larval antigens in 32 sera taken from Iberian ibex from the Sierra Nevada Natural Space (southern Spain). Three antigens were collected: L1OES (from L1 larvae), L2OES (L2), and L3OES (L3). Necropsy was considered as the gold standard. The percentage of ibexes harboring Oestrus spp. larvae was 88%, the mean intensity of parasitism being 16.96 ± 14.96 larvae per parasitized host (range: 2-52). In our sample, first-instar larvae (L1) were found in 9% of ibexes, while 69% of hosts carried L2 larvae and 88% L3 larvae. Positive correlations between L1 and L2 numbers, and between L2 and L3 numbers were detected. The best results with the immunoenzymatic assay were obtained using IgG antibodies against the L1OES antigens (specificity = 89%; sensitivity = 100%; positive predictive value = 100%; negative predictive value = 57%). The IgG seroprevalence against L1OES was 78%. Thus, the analysis of IgG antibodies against antigens collected from L1 O. ovis larvae would seem to be a noninvasive method for reliably diagnosing oestrosis in naturally infested Iberian ibex. Nevertheless, additional immunological and methodological advances are still required because false positive and false negative results still represent a non-negligible part of the results of the ELISA tests.

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).

Analysis of the humoral immune response to Oestrus ovis in ovine

Antibody responses (IgG, IgM and IgA) against Oestrus ovis were analyzed in sheep and in first year grazing lambs from Sardinia (Italy) by an indirect-enzyme-linked immunoassay test and L2 O. ovis excretory/secretory antigens. Serum samples from 208 sheep were obtained prior to be slaughtered, and then heads were removed and cut open along their longitudinal axis to collect the parasites from the nasal cavities, turbinates and sinus. Besides this, blood samples were monthly collected from the lambs of G-1 (maintained under field conditions) and the lambs of G-2 (kept housed since birth to avoid Oestrus infestations) throughout a year. In the sheep, a positive significant correlation was observed between the number of first instar O. ovis larvae and the values of IgM, and between the second instar larvae and the IgG optical densities. In the lambs, all classes of antibodies increased significantly from July in G-1. The highest values of IgG were reached in September (IgG) and decreased in November-December. The IgM response peaked in November, and very low values of IgA were observed during the study. Matching these data with chronobiology of O. ovis in this region, we conclude that the first infection occurs on May, stimulating the production of humoral antibodies. The reduction of the IgG antibody levels starting from October means the beginning of the diapause while the IgM response seems to be associated to the presence of L1 in the nasal cavities. The data obtained led us to forecast an early treatment of the ovine on June-July, which should keep away from the maturation of O. ovis L1 larvae, avoiding the development of clinical lesions and interrupting the life cycle of this parasite.

Analysis of larval antigens of Oestrus ovis for the diagnosis of oestrosis by enzyme-linked immunosorbent assay

A serodiagnostic test for the diagnosis of infestation by the sheep nasal bot fly, Oestrus ovis (Linné) was examined. The enzyme-linked immunosorbent assay (ELISA) technique was used to analyze and compare the production of immunoglobulin G (IgG) antibodies against excretory-secretory products (ESP) and crude extract (CE) antigens from all the different larval stages of O. ovis in the sera of 276 adult sheep sampled in summer (n = 135) and winter (n = 141). ESP from first stage larvae was the most sensitive, coating antigen in winter and ESP from second stage larvae during summer. The most specific values were obtained by ESP against L1 in winter and by CE against L3 in summer. These results show that the stage of larval development has a significant impact on the humoral immune response over the course of a season. A significant correlation (P < 0.001) was found between the number of O. ovis larvae and the serum antibody levels using all differents antigens, except L3 CE. In Spain, where a long favourable period exists for the evolution and development of the different stage larvae between March and November, the ELISA test using L1 ESP antigen during winter and L2 ESP antigen in summer may be used for ovine oestrosis immunodiagnosis.

Haemonchus contortus egg excretion and female length reduction in sheep previously infected with Oestrus ovis (Diptera: Oestridae) larvae

Mixed parasitic infection of animals is a common phenomenon in nature. The existence of one species often positively or negatively influences the survival of the other. Our experimental study was started with the objectives to demonstrate the interaction of Haemonchus contortus and Oestrus ovis in relation to cellular and humoral immune responses in sheep. Twenty-two sheep of Tarasconnais breed (France) were divided into four groups (O, OH, H and C) of five or six animals. Group O and OH received 5 weekly consecutive inoculations with O. ovis L1 larvae (total = 82 L1) in the first phase of the experiment between days 0 and 28. On the second phase, groups OH and H received 5000 L3 of H. contortus on day 48 while group C served as our control throughout the experimental period. Parasitological, haematological, serological and histopathological examinations were made according to standard procedures and all animals were slaughtered at day 95. There was no significant variation in the number and degree of development of O. ovis larvae between the two infected groups. Furthermore, in tissues examined in the upper respiratory tract (nasal septum, turbinate, ethmoide and sinus), group O and OH has responded similarly on the basis of cellular inflammatory responses (blood and tissue eosinophils, mast cells and globule leucocytes (GL)) and serum antibody responses against the nasal bots. This may indicate that the presence of H. contortus in the abomasa of group OH had no marked influence over the development of O. ovis larvae in the upper respiratory tract. On the other hand, we have observed a significantly lower H. contortus female worm length, fecal egg count (FEC) and in utero egg count in animals harbouring the nasal bot (OH) than in the mono-infected group (H). This was significantly associated with higher blood eosinophilia, higher packed cell volume (PCV) and increased number of tissue eosinophils and globule leucocytes. We conclude that, the establishment of O. ovis larvae in the upper respiratory tract has initiated higher inflammatory cellular activity in group OH there by influencing the development and fecundity of H. contortus in the abomasum.

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.

Ectoparasites of livestock in Europe and the Mediterranean region

Arthropod ectoparasites can have a major impact on the productivity and welfare of livestock. In recent years, many parts of Europe have seen important changes in the nature of animal husbandry and parasite control, which have increased the need for a precise understanding of the current distribution and prevalence of livestock ectoparasites. In some cases, these changes have been associated with moves towards increased productivity, such as higher-stocking densities, large-scale rearing units, indoor confinement, reduced genetic diversity and large-scale movement of animals and, in others, with a move towards organic farming. There have also been changes in parasite control, associated with the development of new parasiticides, such as the macrocyclic lactones, and concern over the continued use of some of the older neurotoxic compounds. These changes have been exacerbated by outbreaks of endemic disease, the threats of exotic disease introduction and fears of potential changes in arthropod distribution associated with climate change. This paper therefore, reviews the current status of livestock ectoparasites in Europe and the Mediterranean region.

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.

Chronobiology of Oestrus ovis (Diptera: Oestridae) in Sardinia, Italy: guidelines to chemoprophylaxis

Oestrus ovis (Linné 1761) larvae are obligatory parasites of the nasal and sinus cavities of sheep and goats. Infestation is prevalent in hot and dry regions, such as Mediterranean countries. The current work was developed to establish the chronobiology of O. ovis in Sardinia, to determine the most suitable time for chemoprophylaxis. A survey was carried out during 1998, and sheep heads were collected monthly from local flocks. A total of 443 heads was examined, and the prevalence of oestrosis was 73.8%. We collected 2,691 larvae (mean = 6.07 +/- 9.52), and the intensity was greatest in November. The humoral immune response against the nasal bot fly was analyzed by means of an indirect-ELISA using second-instar O. ovis excretory and secretory antigens. A seasonal variation in the antibody levels was observed, increasing from April and peaked in June and in September. A significant correlation was observed between first instar intensity and the mean relative humidity (r2 = 0.120; P < 0.05), and between second-instar intensity and the mean temperature (r2 = 0.241; P < 0.05). Three periods in the chronobiology of O. ovis were defined: diapause (October-February), the active phase ofthe endogenous cycle (March-September) and the exit phase (May-September). Our results showed that treatment in October-November was suitable, because first instars were in diapause, preventing the development of first into second instars, and second into third instars.