Epidemiology of sheep infection by Oestrus ovis in Algeria

313 sheep were examined in 1996 to assess the importance and seasonal evolution of Oestrus ovis infection in the Algerian region of El-Tarf. Prevalence was found to be 67.4%. The larval burden was 18 larvae by infected sheep. The prevalence was higher in older sheep than in lambs; intensity was similar. The different larval stages were found all along the year in sheep with prevalence ranging from 33.1 to 80.5% for L1, 9.7 to 43.9% for L2 and 8.4 to 23.0% for L3. The sheep were the least infected in winter (prevalence from 35.7 to 44% and intensity seven to ten larvae per sheep). The highest infection was found during the warm season (spring to autumn, prevalence from 62 to 90% and intensity ranging from 15 to 25). This larval evolution profile suggested the existence of one long cycle (November-April) and possibly two shorts cycles (May-October). This epidemiological pattern is similar to that in Morocco but was slightly different from the situation in Tunisia where the winter cycle was apparently of lesser importance.     

Serologic diagnosis of Oestrus ovis (Diptera: Oestridae) in naturally infested sheep

Sera from eighteen control sheep supposed to be free from parasitism by Oestrus ovis Linnaeus, 1761, and from 100 sheep raised in an enzootic area of O.ovis infestations were tested to detect anti-Oestrus antibodies by double immunodiffusion (DD) and indirect haemagglutination (IH) tests with somatic crude antigens from first (L1), second (L2) and third (L3) instar of O.ovis larvae. At necropsy, eighty-eight out of 100 sheep from the O.ovis infested area were found to be parasitized while the eighteen control ovines did not show Oestrus larvae. Examination of the sera from the parasitized sheep by DD showed positive results of 42% for L1, 59% for L2 and 18% for L3. Screening the sera with IH gave sensitivities of 100% for L1, 100% for L2 and 97.7% for L3. Sheep, naturally parasitized by gastrointestinal nematodes, presented no cross immune reactions in DD tests with the three larval stages of O.ovis or with L2 larvae in IH tests.     

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.     

Epidemiology of Oestrus ovis infection of sheep in Argentina's Western Pampas

Seasonal population trends and effects of Oestrus ovis in naturally infected sheep were studied over 13 months, in the Western of the Pampeana region. At weaning, 140 growing lambs were randomly allocated to two groups: UG, untreated group and TG treated every 4 weeks with closantel (10 mg/kg). Successive Oestrus free tracer lambs (TL) by previous treatment (n = 65) were slaughtered after 20-30 exposition days for larval counts. Likewise, other group PL of 117 permanent untreated lambs was slaughtered from four to 17 months of age. Weighing and assessment of health signs of UG and TG and blood samples were monthly carried out. The prevalence of infection in permanent group varied from 33% to 100%. Mean number of larvae in PL was 6.1 with 3 L1, 1.4 L2 and 1.6 L3 during spring-summer and 17.9 with 16.9 L1, 0.5 L2 and 0.4 L3 during autumn-winter months. In PL the proportions of larvae in each of the different larval stages was similar during spring and summer, but a significant (P < 0.01) increase of L1 was detected during autumn and winter. The prevalence in tracer lambs was 100% during summer time and larvae were absent from 25-May to 25-October. Mean larval burdens of positive TL varied from 6.4 to one Oestrus and a significant peak (P < 0.05) of larvae was seen from December to March. Since March to November only L1 was recovered from TL. TG group showed a reduction in nasal discharge and in antibody ELISA levels, but no difference was observed in live weight gain between TG and UG. These results show a high prevalence during summer and that the perpetuation of Oestrus is ensured by an autumn period of arrested development and the over wintering larvae in the sheep heads.     

Hypodermosis of red deer in Spain

From February 1998 to January 1999, 106 red deer in the Autonomic Organism National Park "Quintos de Mora" (Toledo, central Spain) were evaluated to determine the prevalence and dynamics of infection with Hypoderma sp. by detection of subcutaneous larvae. Between six and 13 deer shot in selective hunting were examined monthly. Hypoderma sp. larvae were detected throughout the period except in June, July and August of 1998. Excluding the period during which no subcutaneous larvae were detected, the number of animals sampled was 80 (52 males and 28 females), belonging to three age classes: 12 calves (<1-yr-old), 19 yearlings (1-yr-old), and 49 adults (2- to 10-yr-old). All the third instar (L3) collected were identified as H. actaeon. Total prevalence during the period of larval detection was 61%. Prevalence in yearling and adult deer shot during the official hunting season was 89%. Monthly prevalence increased from September to January and decreased from February to May. In September and October, a small percentage of larvae were classified as first instar (L1). The rest of larvae collected between September and December were second instar (L2). Third instar (L3) predominated in January and February and was the only stage collected from March to May. Intensity ranged from 1 to 145 larvae. Intensities were >100 larvae in 6% of animals. Possible relationships of intensity or prevalence of infection with sex or age of the animals were evaluated. Significant differences in prevalence were observed among different host age classes. Prevalence was higher in yearlings (84%) than in adults (63%) and lowest in calves (17%).     

PCR identification and phylogenetic analysis of the medically important dust mite <Emphasis Type="Italic">Suidasia medanensis</Emphasis> (Acari: Suidasiidae) in Malaysia

Hard ticks are a perennial problem in livestock systems throughout Mexico. No data are currently available on tick prevalence, infestation intensity and population dynamics for sheep in the humid tropics of Mexico. Blackbelly sheep (n = 30) in Tabasco state, Mexico, were examined every 3 weeks for 1 year, and all Ixodidae ticks were counted and removed for analysis. Tick species were identified, infestation prevalence and intensity calculated per animal, and infestation per body zone determined. Overall infestation on the studied animals was 51.9%. Four tick species were identified (Amblyomma mixtum, A. imitator, Rhipicephalus microplus and R. annulatus), the most abundant being A. mixtum (94.9%). Prevalence was highest during the northwinds season (61.9%), followed by the dry (48.5%) and rainy (47.3%) seasons; however, the intensity (2.01–2.07 ticks/sheep) did not differ between seasons. Infestation was most frequent in certain zones including the axilla, crotch, udder, abdomen, thorax and rib area. Sheep in the humid tropics of Tabasco, Mexico, are parasitized by four hard tick species and prevalence is highest in the northwinds season. The present data constitute an important baseline for developing sustainable tick control programs for sheep in the humid tropics of Mexico.     

Parasitism of Hylodes phyllodes (Anura: Cycloramphidae) by Hannemania sp (Acari: Trombicuudae) in an area of Atlantic Forest, Ilha Grande, southeastern Brazil

We studied some parameters of the parasitism by the mite Hannemonia sp. on the endemic frog Hylodes phyllodes in the Atlantic Forest of Ilha Grande (Rio de Janeiro State, Brazil). Prevalence, mean abundance, mean intensity and total intensity of infestation, body regions infected, and host sexual differences in parasitism rate of the larvae of Hannemania sp. on individuals of H. phyllodes were assessed. Prevalence was 86.5% (N = 37; total of 1,745 larvae of Hannemania sp) for male hosts and 91.7% (N = 12; total of 330 larvae) for female hosts, with no significant difference between the sexes. Overall prevalence of Hannemania sp. on H. phyllodes was 87.7%. Mean intensity of infestation in males (54.5 +/- 42.5; range 1-173 larvae) was higher than in females (29.9 +/- 47.6; range 1-166). We conclude that the rates of intensity, abundance, and prevalence of Hannemania larvae parasitizing Hylodes phyllodes at Ilha Grande were considerably high, suggesting that this species of anuran constitutes a relevant host for this mite species to complete its life-cycle in the area. Differences between males and females in infestation rates probably reflect their differential use of space in the forest.     

Sheep and goat immune responses to nose bot infestation: a review

Oestrus ovis L. (Diptera: Oestridae) is a cosmopolitan agent of myiasis in sheep and goats. The parasitic phase begins after adult females deposit first-stage larvae (L1) into the nostrils of hosts; these larvae develop into L2 and L3 in the nasal and sinus horn cavities. Sneezing and nasal discharges are the major clinical signs in infected animals. The pathogenesis of O. ovis infection is caused by: (a) the trauma resulting from the mechanical action of spines and hooks during larval movement on mucosal membranes, and, more importantly, (b) an allergenic reaction provoked by molecules excreted/secreted by larvae, of which salivary antigens are those mainly recognized by the host's immune system. The recruitment of immune reactive cells increases gradually from the nasal to sinus cavities in infected hosts. Mast cells, eosinophils, macrophages and lymphocytes are always more numerous in infected than non-infected animals. Humoral (antibody) systemic response of immunoglobulin G (IgG) usually reaches seroconversion 2-4 weeks post-first infection and the highest levels are observed during the development of L2 and L3 larvae. Local antibody responses include specific IgG, which has been found to negatively correlate with larval survival and development. Hypersensitivity reaction, immunomodulation, immunization trials and mixed infections of O. ovis and helminths are discussed.     

Reactions of cells of nasal and sinusoidal mucosa of goats and sheep naturally infected by Oestrus ovis Linné 1758 (Diptera: Oestridae)]

OEstrosis is a very common myiasis of sheep and goats in mediterranean and tropical countries. Goats are suitable hosts for OEstrus ovis but the parasitic burden remain lower than in sheep. Cellular responses (mucous and serous mast cells, eosinophis and globules leucocytes) were measured in 30 infected and 30 non infected sheep and in 23 infected and 24 non infected goats. The presence of OEstrus ovis larvae led to an important inflammatory response in sheep and in goats as well. Furthermore, the intensity of the cellular response correlated with the larva burden, specially with globules leucocytes and eosinophils. Nevertheless, huge differences occurred between sheep and goats responses even in similar larval burden range. Infected sheep showed larger counts of mucous mast cells than goats, the differences were smaller in serous mast cells and eosinophils and no difference was detected in globules leucocytes (intraepithelial mast cells) counts between the two hosts species. These results were compared with those obtained in gastro-intestinal strongyles infections.     

Three cases of ophthalmomyiasis externa by sheep botfly Oestrus ovis in Italy

Human infection with the sheep nasal botfly Oestrus ovis is sporadic and is often the consequence of an accidental deposit of the larvae by an adult botfly in the eye. This infestation results in external ophthalmomyiasis that, although a very rare condition, is more common among people living close to farming communities. We report three cases of O. ovis infestation which occurred in Italy in a limited area of La Spezia province (Le Cinque Terre), Italy during summer 2004. None of the patients had contact with wild or farm animals.     

Risk factors in habitats of the tick Ixodes ricinus influencing human exposure to Ehrlichia phagocytophila bacteria

Ixodes ricinus L. (Acari: Ixodida) were sampled during 1996-99 in southern Scotland, on vegetation using cloth drags, on humans by removal from clothing and on roe deer (Capreolus capreolus L.) by searching legs of culled deer. Developmental microclimate was recorded by automatic recorders and questing microclimate by portable instruments during tick collections. Ticks and deer were examined for infection with Ehrlichia phagocytophila bacteria (Rickettsiales) using microscopy and polymerase chain reaction. This pathogen causes tick-borne fever of sheep in Europe and human granulocytic ehrlichiosis in North America, but in Europe human clinical ehrlichiosis due to E. phagocytophila has not been recorded despite serological evidence of exposure. Among three types of habitat, coniferous woodland was most infested with questing ticks (560 ticks/km of drag; mean numbers collected on long trousers: 24.3 larvae, 13.5 nymphs and 0.8 adult ticks/km walked), deciduous woodland had slightly lower infestation (426 ticks/km drag) and upland sheep pasture had much lower infestation (220 ticks/km drag). Of the three main vegetation types, bracken was least infested (360 ticks/km drag), ericas most (430 ticks/km drag) and grassland had intermediate infestation density (413 ticks/km drag). Questing and developmental microclimates were poor predictors of exposure within these habitats, except lower infestation of pastures was attributed to greater illumination there. Collectors who walked a total of 300 km through all habitats (taking 360 h in all seasons), wearing cotton trousers hanging outside rubber boots, were bitten by only four nymphs and 11 larvae of I. ricinus (but no adult ticks). There was a negative correlation between densities of deer and ticks collected, although presence of deer remains a major indicator of exposure. The proportion of infected ticks was fairly uniform at four sites studied. Overall prevalence of E. phagocytophila in I. ricinus was 3.3% in nymphs (40/1203) but only approximately 1.5% in adults of both sexes (although males do not bite). It was estimated that nymphs of I. ricinus gave 4.4% probability of one infected bite/person/year (for occupational exposure during this research) due to presence in all seasons and habitats, their human biting rate of 0.011 nymphs/h or 0.013 nymphs/km and widespread infection with E. phagocytophila. The frequency distribution of intensity of infection in ticks was approximately normal (mean 98 morulae/nymph infected), thus there is a high risk of receiving a high dose from any one infected tick bite.     

Survival of the larvae of the ship botfly Oestrus ovis L. depending on the function of the immune system of the host's body

In the experiments on artificial infection the survival of larvae of Oestrus ovis L. in sheep with depressed, normal and stimulated immune system was studied. The maximum number of larvae survived in immune depressed animals (62.9%), the minimum number survived in immune stimulated animals (0.4%). For the estimation of specific immune response the reaction of indirect hemagglutination (IHA), the reaction of diffused precipitation (RDP) and the immune ferment analysis (ELISA) were used.     

The kinetics of specific serum antibodies in sheep infested with sheep bot larvae]

The kinetics of specific antibodies of the blood serum of sheep experimentally infested with 80, 160 and 1000 specimens of Oestrus ovis larvae was examined. The affinity pure serum IgG and the immunoferment analysis (ELISA) were used for qualitative estimation of specific antibodies. It has been shown that the level of specific antibodies correlates with the larval biomass and is connected with ontogenesis of this parasite. The younger animals, which were infested for the first time, are characterized by more intensive production of specific IgG than adult reinfested ones. The ways of immunity response formation in animals infested with Oestrus ovis larvae are considered.     

Acquired resistance of sheep to larvae of Lucilia cuprina, assessed in vivo and in vitro

The effect on subsequent larval survival of infesting sheep repeatedly with larvae of Lucilia cuprina was assayed in vivo and in vitro. One in vivo assay technique, in which implanted larvae were grown to third instar, indicated a significant reduction in larval survival; another in vivo technique, in which larvae were allowed to develop to second instar in small aluminium rings attached to the sheep, indicated no reduction in larval growth or survival. Larvae of Lucilia cuprina grown in vitro on media containing sera from previously infested sheep were significantly retarded in growth after 20 h compared with controls; no difference was detected when larvae were allowed to develop to pupation on two changes of the same media. No significant differences in survival of larvae either to 20 h or to pupation were obtained between the two treatments. ELISA antibody levels against crude soluble larval material were significantly higher for sera from infested sheep than for control sera, and the regression of antibody level on mean larval weight obtained after 20 h growth in vitro was significant. The immunoglobulin fraction isolated from sera of infested sheep significantly retarded larval growth when incorporated with normal serum in growth media. These results are consistent with an effect of specific anti-larval antibody produced by sheep in response to infestation.     

Bird ticks in an area of the Cerrado of Minas Gerais State, southeast Brazil

In the present study the tick prevalence, mean intensity of infestation and species were recorded on birds captured between January 2009 and December 2010 in the Ecological Station Pirapitinga-ESEC from Minas Gerais State, Brazil. A total of 967 birds, from 15 families and 40 species were captured and 165 (17.1 %) individuals were parasitized by ticks. Of these 160 (97 %) belonged to the order Passeriformes. Five tick species were identified: Amblyomma longirostre (n = 274) was the most common species followed by Amblyomma parvum (n = 43), Amblyomma nodosum (n = 39), Amblyomma ovale (n = 24) and Riphicephalus sanguineus (n = 7). None of 61 unengorged larvae molted to nymph. The mean intensity of infestation was 2.7 ± 2.4 ticks per bird (448 ticks/165 birds) ranging from 1 to 10. Only 19 (11.4 %) birds were infested with one species of tick. The remaining birds were infested by two, three or four species of ticks. Also new hosts for all five ticks were recorded. Only nymphs were recorded throughout the year with two similar peaks during autumn and winter 2009 and 2010.     

Occurrence and larval growth of Hypoderma lineatum in the oesophagi of cattle from northwest Spain: influence of geographical and climatic conditions

From March 2004 to March 2005, 862 bovine oesophagi were collected at weekly intervals from a slaughterhouse in Lugo in northwest Spain in order to establish the occurrence and chronobiology of the first-instar (L1) oesophageal phase of Hypoderma lineatum (De Villers) (Diptera: Oestridae) in different climatic areas from this region. First instars were observed in oesophagi from May to February (10 months/year). The annual prevalence was 18.2%. Maximum prevalence occurred in July and October. Prevalence in the coastal area was significantly lower than in the other areas. A total of 846 L1s were extracted from 120 infested oesophagi, 814 from the submucosa and 32 from external locations. The mean intensity of infestation was low (7.6 +/- 6.2); only 3.3% of the oesophagi harboured more than 30 L1s. Maximum numbers of L1/animal were observed in November and January. There were no differences in intensity of infection between climatic areas. The length of L1s ranged from 4.6 +/- 0.86 mm in May to 14.6 +/- 1.04 mm in January. The growth of larvae collected from external sites was parallel to those found in the submucosa. Mountainous areas produced the L1s of greatest length, followed by central and transition zones and, finally, coastal zones. To avoid adverse reactions resulting from the application of systemic insecticides, it will be necessary to adjust the time at which cattle are treated according to geographical or climatic area.     

Population dynamics of Pomphorhynchus bulbocolli in Gammarus pseudolimnaeus

The population dynamics of larval Pomphorhynchus bulbocolli were studied in the amphipod intermediate host, Gammarus pseudolimnaeus. Amphipods were collected monthly from April 1982 to March 1983 from a study site at the West Fork of Drake's Creek, Simpson Co., Kentucky. The number of infected amphipods per m2 was lowest (0.6) in May and highest (27.3) in November. A total of 2,502 amphipods was examined; 1,575 (62.9%) were infected with P. bulbocolli. Infection intensity ranged from 1 to 12 with a mean of 1.83 +/- 0.03. Single and multiple worm infections were found in 800 (50.8%) and 775 (49.2%) amphipods, respectively. Female amphipods had higher prevalence and intensity of infections than males but differences were not significant. Prevalence in the monthly samples was lowest in May (5.1%) and highest in October (88.1%). The monthly mean intensity of infection was lowest in July (1.10 +/- 0.04) and highest in November (2.02 +/- 0.08). Amphipods in length classes 3 through 15 were infected with P. bulbocolli. In late summer and fall, amphipods in all length classes were infected, while in late winter and spring only large amphipods were infected. Recruitment of P. bulbocolli into amphipods was seasonal and the total infrapopulation within an amphipod was usually acquired at one time. There was little correlation between size and number of larvae present.     

Population biology and behavior of larval Eustrongylides tubifex (Nematoda: Dioctophymatida) in poikilothermous hosts

A total of 178 channel catfish (Ictalurus punctatus), 162 freshwater drum (Aplodinotus grunniens), 60 smallmouth bass (Micropterus dolomieui) and 2,488 yellow perch (Perca flavescens) were examined for larval Eustrongylides tubifex (Nitzsch 1819) J?gerskiold 1909 during 1973 and 1974. Older, large fish exhibited higher prevalence, larger mean numbers of larvae in infected fish, larger mean numbers of larvae in all fish examined, and wider range of intensity of infection. Infections were most extensive in yellow perch. The majority of larvae were removed from mesenteric cysts. Under experimental conditions, larvae migrated from cysts through the body wall when environmental temperatures reached or exceeded 40 C. Fourth-stage larvae removed from yellow perch successfully reinfected a variety of poikilothermous experimental hosts. Both young-of-the-year and I+ age/size class yellow perch exhibited increasing monthly larval worm burdens during portions of the sampling period. Older (II+) age/size class yellow perch did not exhibit significantly increasing worm burdens. No significant differences were noted in numbers of male and female larvae or in worm burdens in male and female yellow perch.     

Development and pathogenesis of Parelaphostrongylus odocoilei (nematoda: protostrongylidae) in experimentally infected thinhorn sheep (Ovis dalli )

Recently, the protostrongylid nematode Parelaphostrongylus odocoilei has been reported in a new host species, thinhorn sheep (Ovis dalli). For the first time, we completed the life cycle of P. odocoilei in three Stone's sheep (O. dalli stonei) and two thinhorn hybrids (O. dalli stonei x O. dalli dalli), each infected with 200 third-stage larvae from slugs (Deroceras laeve). The prepatent period ranged from 68 days to 74 days, and shedding of first-stage larvae (L1) peaked at >10,000 L1 per gram of feces between 90 and 110 days postinfection. A total of 75, 27, and 14 adult P. odocoilei were recovered from skeletal muscles of three Stone's sheep. Starting in the prepatent period, all infected sheep lost weight and developed peripheral eosinophilia. At 2 wk before patency, two thinhorn hybrids developed neurologic signs (hind end ataxia, loss of conscious proprioception, and hyperesthesia) that resolved at patency. Eosinophilic pleocytosis and antibody to Parelaphostrongylus spp. were detected in the cerebrospinal fluid of the affected sheep, suggesting that the migration route of the "muscleworm" P. odocoilei may involve the central nervous system. Twenty days after treatment with ivermectin, neurologic signs recurred and larval shedding ceased in one infected thinhorn hybrid, whereas multiple treatments transiently suppressed but did not eliminate larval shedding in the other. During patency, two Stone's sheep with numerous eggs and larvae of P. odocoilei in the lungs died of respiratory failure following anesthesia or exertion. Parelaphostrongylus odocoilei has widespread geographic distribution, high prevalence, the possibility of causing neurologic and respiratory disease, resistance to treatment, and may constitute a significant emerging disease risk for thinhorn sheep.     

Distribution of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) in tomato fields and its relationship to weather factors

A survey was conducted in tomato fields at different localities to assess the distribution of tomato fruitworm Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) in Punjab Province, Pakistan. The effect of weather factors on its population was also investigated. Eleven tomato-growing districts were selected and data for larval population and fruit infestation were recorded. The maximum larval population (5.2 larvae/plant) of H. armigera was recorded in Bahawalpur district with 32.6% fruit infestation. However, the minimum larval population (1.4 larvae/plant) inflicted 14.7% fruit infestation in Rawalpindi district. The temperature was positively correlated while relative humidity showed negative interaction with the larval population and fruit infestation.