RESUMO
Among the diseases which can afflict the nasal cavities of small ruminants, oestrosis stands out. In Brazil, more specifically in its South-East region, the reports are limited only to the State of São Paulo and to the municipality of Araxá, Minas Gerais. Therefore, it has been sought to assess the parasitic prevalence of Oestrus ovis in sheep farmed in the municipality of Ituiutaba, Minas Gerais-Brazil, while correlating the larval size and stage, and its anatomical localization. Eighty-eight hemiheads of healthy Santa Inês/Dorper crossbreds Ovis aries have been used at random. The larvae in view were then collected and fixated to be quantified and analyzed in regard of size and stage of development. It is concluded that the oestrosis is an existing problem in the municipality of Ituiutaba, this being the first complete study on the prevalence of this parasite in the State of Minas Gerais. By anatomical distribution, only the differences of total larval averages between the frontal sinus and the ventral nasal meatus, the common nasal meatus and the nasopharynx have been significant. In size, the significant difference has been there only upon comparison between the size and the larval stage, information that is crucial for a better understanding of the cyclic progression, of the clinical symptomatology, and animal prophylaxis.
Dentre as doenças que podem atingir as cavidades nasais dos pequenos ruminantes, destaca-se a oestrose. No Brasil, mais especificamente na região Sudeste, os relatos estão limitados ao estado de São Paulo e ao município de Araxá, Minas Gerais. Assim, procurou-se avaliar a prevalência parasitária do Oestrus ovis em ovinos criados no município de Ituiutaba, Minas Gerais-Brasil, correlacionando ao mesmo tempo o tamanho e estágio larval com a sua localização anatômica. Oitenta e oito hemicabeças de Ovis aries mestiços Santa Inês com Dorper saudáveis foram utilizadas aleatoriamente. As larvas visualizadas foram então coletadas e fixadas para serem quantificadas e analisadas em relação ao seu tamanho e estágio de desenvolvimento. Conclui-se que a oestrose é um problema existente no município de Ituiutaba, sendo este o primeiro estudo completo sobre a prevalência deste parasito no estado de Minas Gerais. Por distribuição anatômica, apenas as diferenças das médias larvais totais entre o seio frontal e o meato nasal ventral, meato nasal comum e a nasofaringe foram significativas - o que confirma a preferência das larvas por essa região. Em tamanho, a diferença significativa só ocorreu mediante a comparação entre o tamanho e estágio das larvas, informação crucial para uma melhor compreensão da progressão cíclica, sintomatologia clínica e profilaxia dos animais.
Assuntos
Animais , Doenças dos Ovinos/parasitologia , Dípteros/parasitologia , Miíase/etiologia , Miíase/veterinária , Miíase/epidemiologia , Doenças dos Seios Paranasais/parasitologia , Doenças dos Seios Paranasais/veterinária , Brasil/epidemiologia , Cavidade Nasal/parasitologiaRESUMO
Abstract We report the occurrence and infection parameters of two species of nasal mites in Passer domesticus (Linnaeus, 1758) (house sparrow). Nasal passages, trachea, lungs, and air sacs of 100 house sparrows captured in an urban area at the city of Pelotas, State of Rio Grande do Sul, southern Brazil, were examined with a stereomicroscope. The mite, Sternostoma tracheacolum Lawrence, 1948 was present in the trachea and/or lungs (or both) of 13 birds (13%) at a mean intensity of 6.7 mites/infected host. Ptilonyssus hirsti (Castro & Pereira, 1947) was found in the nasal cavity of 1 sparrow (1%); coinfection was not observed in this bird. There was no significant difference in the prevalence and mean intensity of infection of S. tracheacolum between male and female birds. To our knowledge, this is the first study reporting the occurrence of S. tracheacolum in P. domesticus in Brazil and the presence of P. hirsti in P. domesticus from Rio Grande do Sul, Brazil. This is the first survey to provide the infection parameters of each of these mites in house sparrows.
Resumo O objetivo deste estudo foi relatar duas espécies de ácaros nasais parasitos do sistema respiratório de Passer domesticus (Linnaeus, 1758) (pardal) e seus respectivos índices parasitológicos. Para isso, foram examinados ao estereomicroscópio, cavidade nasal, traqueia, pulmão e sacos aéreos de 100 pardais capturados na área urbana de Pelotas, Rio Grande do Sul, Brasil. Sternostoma tracheacolum Lawrence, 1948 ocorreu na traqueia e/ou pulmão de 13 aves (13%) com intensidade média de 6,7 ácaros/hospedeiro infectado e Ptilonyssus hirsti (Castro & Pereira, 1947) na cavidade nasal de um único pardal (1%), não havendo coinfecção. A prevalência e intensidade média de infecção por S. tracheacolum entre hospedeiros machos e fêmeas não apresentou diferença significativa. Este relato caracteriza o primeiro registro de S. tracheacolum parasitando P. domesticus no Brasil e de P. hirsti em pardais no RS, Brasil, e seus respectivos índices de infecção.
Assuntos
Animais , Masculino , Feminino , Doenças das Aves/parasitologia , Pardais/parasitologia , Ácaros/classificação , Doenças das Aves/epidemiologia , Brasil/epidemiologia , Prevalência , Cavidade Nasal/parasitologiaRESUMO
Parasitological examination of the maya needlefish Strongylura hubbsi Collette (Belonidae) from the Rio Lacantún basin in the Montes Azules Biosphere Reserve, Chiapas, Mexico showed that specimens were parasitized by two monogenean species in two different sites: Paracolpenteron hubbsii n. gen., n. sp in the urinary bladder and Ancyrocephalus chiapanensis n. sp in the gill lamellae. Paracolpenteron hubbsii differs from other dactylogyrid species without a haptoral anchor/bar complex infecting the urinary systems, gills and nasal cavities by the general morphology of hooks, a dextral vaginal opening, a tubular male copulatory organ comprising a base from which a coiled shaft arises in counterclockwise direction, and an unarticulated Y-shaped accessory piece. Ancyrocephalus chiapanensis n. sp. resembles Ancyrocephalus cornutus William & Rogers, 1972 from the gills of Strongylura marina from Florida from which it differs in possessing a twisted tube of the male copulatory organ (curved in A. cornutus), ventral bar with cavities on the ends (cavities absent in A. cornutus) and by the size of the ventral (length 31-34 µm vs. 24-27 µm in A. cornutus) and dorsal (length 25-28 µm vs. 18-22 µm in A. cornutus) anchors. These new monogeneans are described herein and their biogeography is briefly discussed based on the previous phylogenetic hypotheses concerning the host family.
Assuntos
Beloniformes/parasitologia , Doenças dos Peixes/parasitologia , Brânquias/parasitologia , Trematódeos/isolamento & purificação , Infecções por Trematódeos/veterinária , Bexiga Urinária/parasitologia , Animais , Diagnóstico Diferencial , Feminino , Genitália Feminina , Genitália Masculina , Masculino , México/epidemiologia , Cavidade Nasal/parasitologia , Filogenia , Filogeografia , Trematódeos/anatomia & histologia , Trematódeos/classificação , Infecções por Trematódeos/parasitologiaRESUMO
We report the occurrence and infection parameters of two species of nasal mites in Passer domesticus (Linnaeus, 1758) (house sparrow). Nasal passages, trachea, lungs, and air sacs of 100 house sparrows captured in an urban area at the city of Pelotas, State of Rio Grande do Sul, southern Brazil, were examined with a stereomicroscope. The mite, Sternostoma tracheacolum Lawrence, 1948 was present in the trachea and/or lungs (or both) of 13 birds (13%) at a mean intensity of 6.7 mites/infected host. Ptilonyssus hirsti (Castro & Pereira, 1947) was found in the nasal cavity of 1 sparrow (1%); coinfection was not observed in this bird. There was no significant difference in the prevalence and mean intensity of infection of S. tracheacolum between male and female birds. To our knowledge, this is the first study reporting the occurrence of S. tracheacolum in P. domesticus in Brazil and the presence of P. hirsti in P. domesticus from Rio Grande do Sul, Brazil. This is the first survey to provide the infection parameters of each of these mites in house sparrows.
Assuntos
Doenças das Aves/parasitologia , Ácaros/classificação , Pardais/parasitologia , Animais , Doenças das Aves/epidemiologia , Brasil/epidemiologia , Feminino , Masculino , Cavidade Nasal/parasitologia , PrevalênciaRESUMO
Dactylogyridae is overwhelmingly the most abundant and diverse taxon among monogeneans in continental waters of South America. Their small body size requires considerable sampling effort and training for collecting and identifying the worms from the gills, skin, nasal cavities, and other microhabitats. Indeed, diagnostic characteristics as sclerites and male copulatory complex are generally less than 100-µm long and are essential for taxonomic description and identification of species. Here, a combination of simple and routine methods for three-dimensional morphological studies on hard structures is proposed for dactylogirids: SDS treatment for clarification of specimens and enzymatic digestion with proteinase K for freeing sclerotized structures, followed by laser confocal microscopy. This method is applicable to fresh or fixed specimens and does not require staining or dehydration. Indeed, stable autofluorescence emission is detectable at 500-530 nm for bars, anchors, and male copulatory complex when excited by argon laser. Advantages of this protocol over previous methodologies for taking laser confocal images are discussed. Open access software for image processing was used for three-dimensional reconstruction of sclerotized structures generating models and full 360° rotation videos.
Assuntos
Caraciformes/parasitologia , Doenças dos Peixes/parasitologia , Trematódeos/classificação , Infecções por Trematódeos/veterinária , Animais , Brânquias/parasitologia , Processamento de Imagem Assistida por Computador , Imageamento Tridimensional/veterinária , Lagos , Masculino , Microscopia Confocal/veterinária , Cavidade Nasal/parasitologia , Rios , América do Sul , Trematódeos/isolamento & purificação , Trematódeos/ultraestrutura , Infecções por Trematódeos/parasitologiaRESUMO
A total of 81 Tyraniidae birds were examined, 80 Pitangus sulphuratus (Linnaeus, 1766) (Great kiscadee), and one Machetornis rixosa (Vieilot, 1819) (Cattle tyrant), for collection of nasal mites, which were identified as Ptilonyssus spinosus (Brooks & Strandtmann, 1960) and Sternostoma longisetosae (Hyland, 1961) (Rhinonyssidae). This finding characterises the first report of P. spinosus and S. longisetosae in P. sulphuratus, and the first record of P. spinosus in M. rixosa, and expands the geographic distribution of these species. It is the first occurrence of S. longisetosae in the Neotropics, and the first citation of P. spinosus in the state of Rio Grande do Sul, Brazil.
Assuntos
Ácaros/classificação , Cavidade Nasal/parasitologia , Passeriformes/parasitologia , Animais , Brasil , Feminino , Masculino , Passeriformes/classificaçãoRESUMO
A new species of Rhinonastes, hitherto monotypic, is described and illustrated from the nasal cavity of 'curimat', Prochilodus argenteus from São Francisco River, Brazil. Rhinonastes curimatae n. sp. presents a male copulatory organ with more than five rings while the type species of the genus is characterized by male copulatory organ with less than two rings. This is the first record of a nasal parasite in P. argenteus.
Assuntos
Caraciformes/parasitologia , Doenças dos Peixes/parasitologia , Platelmintos/isolamento & purificação , Animais , Brasil , Ectoparasitoses , Água Doce , Brânquias/parasitologia , Masculino , Cavidade Nasal/parasitologia , Platelmintos/anatomia & histologia , Platelmintos/classificação , RiosRESUMO
A total of 81 Tyraniidae birds were examined, 80 Pitangus sulphuratus (Linnaeus, 1766) (Great kiscadee), and one Machetornis rixosa (Vieilot, 1819) (Cattle tyrant), for collection of nasal mites, which were identified as Ptilonyssus spinosus (Brooks & Strandtmann, 1960) and Sternostoma longisetosae (Hyland, 1961) (Rhinonyssidae). This finding characterises the first report of P. spinosus and S. longisetosae in P. sulphuratus, and the first record of P. spinosus in M. rixosa, and expands the geographic distribution of these species. It is the first occurrence of S. longisetosae in the Neotropics, and the first citation of P. spinosus in the state of Rio Grande do Sul, Brazil.
Foram examinadas 81 aves Tyraniidae, 80 Pitangus sulphuratus (Linnaeus, 1766) (Bem-te-vi) e um Machetornis rixosa (Vieilot, 1819) (Suiriri-cavaleiro) para coleta de ácaros nasais, os quais foram identificados como Ptilonyssus spinosus (Brooks & Strandtmann, 1960) e Sternostoma longisetosae (Hyland, 1961) (Rhinonyssidae). Este achado caracteriza o primeiro relato de P. spinosus e S. longisetosae em P. sulphuratus e o primeiro registro de P. spinosus em M. rixosa, e amplia a distribuição geográfica destas espécies, sendo a primeira ocorrência de S. longisetosae na região neotropical e primeira citação de P. spinosus no Rio Grande do Sul, Brasil.
Assuntos
Animais , Feminino , Masculino , Ácaros/classificação , Cavidade Nasal/parasitologia , Passeriformes/parasitologia , Brasil , Passeriformes/classificaçãoRESUMO
A total of 81 Tyraniidae birds were examined, 80 Pitangus sulphuratus (Linnaeus, 1766) (Great kiscadee), and one Machetornis rixosa (Vieilot, 1819) (Cattle tyrant), for collection of nasal mites, which were identified as Ptilonyssus spinosus (Brooks & Strandtmann, 1960) and Sternostoma longisetosae (Hyland, 1961) (Rhinonyssidae). This finding characterises the first report of P. spinosus and S. longisetosae in P. sulphuratus, and the first record of P. spinosus in M. rixosa, and expands the geographic distribution of these species. It is the first occurrence of S. longisetosae in the Neotropics, and the first citation of P. spinosus in the state of Rio Grande do Sul, Brazil.(AU)
Foram examinadas 81 aves Tyraniidae, 80 Pitangus sulphuratus (Linnaeus, 1766) (Bem-te-vi) e um Machetornis rixosa (Vieilot, 1819) (Suiriri-cavaleiro) para coleta de ácaros nasais, os quais foram identificados como Ptilonyssus spinosus (Brooks & Strandtmann, 1960) e Sternostoma longisetosae (Hyland, 1961) (Rhinonyssidae). Este achado caracteriza o primeiro relato de P. spinosus e S. longisetosae em P. sulphuratus e o primeiro registro de P. spinosus em M. rixosa, e amplia a distribuição geográfica destas espécies, sendo a primeira ocorrência de S. longisetosae na região neotropical e primeira citação de P. spinosus no Rio Grande do Sul, Brasil.(AU)
Assuntos
Animais , Masculino , Feminino , Ácaros/classificação , Cavidade Nasal/parasitologia , Passeriformes/parasitologia , Brasil , /classificaçãoRESUMO
Introducción. Las miasis hospitalarias son entidades con una importancia manifiesta en salud pública. La documentación de este tipo de casos es escasa en la literatura biomédica regional y mundial. Objetivo. Informar un caso de miasis hospitalaria en Costa Rica, donde el agente etiológico implicado fue Lucilia cuprina (Diptera: Calliphoridae). Este caso de miasis hospitalaria figura como el primer informe para Latinoamérica asociado con este agente etiológico. Presentación del caso. Una paciente de 91 años de edad, con signos de inmunosupresión, afectación grave de la función pulmonar y asistencia respiratoria mecánica, presentó larvas en ambas fosas nasales al séptimo día después del ingreso hospitalario. Varios ejemplares fueron recolectados y procesados para su identificación. La identificación taxonómica de los ejemplares recolectados estableció que la especie de los muscomorfos correspondía a L. cuprina. Conclusión. El presente constituye el primer caso de miasis hospitalaria por L. cuprina en la literatura biomédica de Costa Rica y el primero registrado en Latinoamérica.
Introduction. Nosocomial myiases can be an important condition from a public health perspective. However, cases of this condition reported in regional and worldwide biomedical literature are scarce. Objective. A case of nosocomial myiasis is reported from Costa Rica, where the species involved was Lucilia cuprina (Diptera: Calliphoridae). Materials and methods. A 91-year-old patient with signs of immunosuppression, severe impairment of lung function, and mechanical ventilation presented larvae in both nostrils on the seventh day after admission. Five specimens were collected and processed for identification. Results. The taxonomic identification of the specimens established that the muscoid fly species was L. cuprina. Conclusion. This is the first case of nosocomial myiasis reported from Costa Rica and in Latin America for which the etiological agent is L. cuprina.
Assuntos
Idoso de 80 Anos ou mais , Animais , Feminino , Humanos , Infecção Hospitalar/parasitologia , Dípteros/crescimento & desenvolvimento , Miíase/diagnóstico , Injúria Renal Aguda/complicações , Broncopneumonia/complicações , Costa Rica/epidemiologia , Evolução Fatal , Moscas Domésticas/crescimento & desenvolvimento , Hospedeiro Imunocomprometido , Controle de Insetos , Larva , Miíase/epidemiologia , Miíase/parasitologia , Cavidade Nasal/parasitologia , Respiração Artificial , Insuficiência Respiratória/complicações , Insuficiência Respiratória/terapiaRESUMO
INTRODUCTION: Nosocomial myiases can be an important condition from a public health perspective. However, cases of this condition reported in regional and worldwide biomedical literature are scarce. OBJECTIVE: A case of nosocomial myiasis is reported from Costa Rica, where the species involved was Lucilia cuprina (Diptera: Calliphoridae). MATERIALS AND METHODS: A 91-year-old patient with signs of immunosuppression, severe impairment of lung function, and mechanical ventilation presented larvae in both nostrils on the seventh day after admission. Five specimens were collected and processed for identification. RESULTS: The taxonomic identification of the specimens established that the muscoid fly species was L. cuprina. CONCLUSION: This is the first case of nosocomial myiasis reported from Costa Rica and in Latin America for which the etiological agent is L. cuprina.
Assuntos
Infecção Hospitalar/parasitologia , Dípteros/crescimento & desenvolvimento , Miíase/diagnóstico , Injúria Renal Aguda/complicações , Idoso de 80 Anos ou mais , Animais , Broncopneumonia/complicações , Costa Rica/epidemiologia , Evolução Fatal , Feminino , Moscas Domésticas/crescimento & desenvolvimento , Humanos , Hospedeiro Imunocomprometido , Controle de Insetos , Larva , Miíase/epidemiologia , Miíase/parasitologia , Cavidade Nasal/parasitologia , Respiração Artificial , Insuficiência Respiratória/complicações , Insuficiência Respiratória/terapiaRESUMO
With the aim of identifying the species of nasal mites of Paroaria coronata (red-crested cardinal), the nasal cavity of 40 birds were examined. The nasal mites were identified as Ptilonyssus sairae de Castro and Sternostoma pirangae Pence, with 50% and 7.5% of prevalence, respectively. This is the first record of these mite species parasitizing P. coronata. This report also amplifies the area of occurrence of S. pirangae for Brazil and that of P. sairae for Rio Grande do Sul, Brazil.
Assuntos
Ácaros , Cavidade Nasal/parasitologia , Passeriformes/parasitologia , Animais , BrasilRESUMO
Infrapopulation genetic variation of the oioxenous, hermaphroditic flatworm Nasicola klawei (Monogenea: Capsalidae) infecting the nasal cavities of nine yellowfin tuna, Thunnus albacares, from the Gulf of Mexico was analyzed using the first internal transcribed spacer (ITS1) single strand conformation polymorphism (SSCP), ITS1 sequencing, and amplified fragment length polymorphism (AFLP). Of a total of 32 worms, six had unique ITS1-SSCP types and the rest was grouped by three types. Two worms of the same infrapopulation shared an ITS1-SSCP type in nine instances but no infrapopulation was monophyletic by ITS1-SSCP analysis. ITS1 sequences (420 bp) varied by 1-11 (0.2-2.6%) nucleotides. Twenty-three AFLP profiles of 80-110 bands failed to support genomic monophyly of any N. klawei infrapopulation. 28S rDNA (990 bp) sequences from four worms representing four infrapopulations were identical and matched conspecific GenBank sequences. Concordant ITS1-SSCP and AFLP analyses indicated that these N. klawei infrapopulations principally resulted from tuna being repeatedly colonized by planktonic, infective larvae (oncomiracidia) rather than by a single host colonization followed by parasite maturation, self-fertilization, and production of auto-infecting progeny.
Assuntos
DNA Espaçador Ribossômico/genética , Doenças dos Peixes/parasitologia , Cavidade Nasal/parasitologia , Polimorfismo Conformacional de Fita Simples/genética , Trematódeos/genética , Atum/parasitologia , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Animais , Impressões Digitais de DNA , DNA Ribossômico/genética , Bases de Dados Genéticas , Golfo do México , México , Filogenia , Autofertilização/fisiologia , Trematódeos/classificação , Trematódeos/isolamento & purificaçãoRESUMO
With the aim of identifying the species of nasal mites of Paroaria coronata (red-crested cardinal), the nasal cavity of 40 birds were examined. The nasal mites were identified as Ptilonyssus sairae de Castro and Sternostoma pirangae Pence, with 50 percent and 7.5 percent of prevalence, respectively. This is the first record of these mite species parasitizing P. coronata. This report also amplifies the area of occurrence of S. pirangae for Brazil and that of P. sairae for Rio Grande do Sul, Brazil.
Assuntos
Animais , Ácaros , Cavidade Nasal/parasitologia , Passeriformes/parasitologia , BrasilRESUMO
During an investigation of the biodiversity and structure of parasite communities among native populations of the erythrinid fish Hoplias malabaricus (Characiformes) from 7 rivers in Brazil, the following monogenoidean (Dactylogyridae) species were found: Urocleidoides malabaricusi n. sp., Urocleidoides naris n. sp., Urocleidoides cuiabai n. sp., Urocleidoides brasiliensis n. sp., and Urocleidoides eremitus Kritsky, Thatcher, and Boeger, 1986. Specimens considered as a new genus of Dactylogyridae were also found. The new species are mainly distinguished from the other 14 species of Urocleidoides in the general morphology of their copulatory and anchors/bar complexes. These new species and the new dactylogyrid genus are described, as well as supplemental observations and new illustrations of U. eremitus are provided. The present findings expand the known geographical distribution of species of Urocleidoides to southeastern and midwestern Brazil. A high speciation of this genus in the tropics is hypothesized, and it is briefly discussed.
Assuntos
Doenças dos Peixes/parasitologia , Brânquias/parasitologia , Cavidade Nasal/parasitologia , Platelmintos/classificação , Infecções por Trematódeos/veterinária , Animais , Brasil , Peixes , Água Doce , Platelmintos/anatomia & histologia , Platelmintos/isolamento & purificação , Infecções por Trematódeos/parasitologiaRESUMO
Two species of Nasicola Yamaguti, 1968 are described from the nasal cavities of tunas ( Thunnus spp.) from off the coast of Brazil: N. brasiliensis n. sp. from T. obesus (Lowe) and the type-species, N. klawei (Stunkard, 1962), from T. albacares (Bonn.). The new species is differentiated from N. klawei on the basis of the large number of testes and from N. hogansi Wheeler & Beverley-Burton, 1986 by its greater body-size, proportionately smaller haptor and smaller number of marginal spines. The host-specificity of Nasicola spp. is commented upon.
Assuntos
Trematódeos/anatomia & histologia , Atum/parasitologia , Animais , Brasil , Feminino , Masculino , Microscopia Eletrônica de Varredura , Cavidade Nasal/parasitologiaRESUMO
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.