RESUMO
Rainfall incidence as a risk factor for umbilical myiasis by Cochliomyia hominivorax in newborn beef cattle and the preventive and curative efficacies of injectable and topical products against its larvae were evaluated. The prevalence of navel myiasis did not differ between sex, however, it did differ between seasons of the year, independent of animal sex, with it being higher in the rainy season than in the dry season for both sexes (males 64.6%, females 62.1%). During the rainy season, rains occurred intermittently and the number of rainy days in a week had a direct influence on prevalence, with an increase (≥87%) in the number of calves with navel myiasis caused by C. hominivorax. When it rained intermittently for four, five and six days in a week during the rainy season, calves had ≈12, 24 and 11 times greater chances, respectively, of having navel myiasis compared to a week without rain during the rainy season. The injectable products did not reach preventive efficacies higher than 35%, while all treatments of topic products reached 100% preventive efficacy at 10 days post-treatment. Only the formulations with 30% dichlorfenthion and 0.32% fipronil achieved 100% curative efficacy. The results reinforce the need for intensified inspection and healing of the umbilicus during the rainy season, mainly during rainier weeks. Furthermore, topical formulations may be a better alternative as a preventive treatment than avermectin formulations. However, the curative efficacy of the topical product containing dichlorvos did not demonstrate a relationship with preventive efficacy for newborn calves.
Assuntos
Dípteros , Miíase , Infecção por Mosca da Bicheira , Masculino , Feminino , Bovinos , Animais , Antiparasitários/uso terapêutico , Umbigo , Infecção por Mosca da Bicheira/tratamento farmacológico , Infecção por Mosca da Bicheira/prevenção & controle , Infecção por Mosca da Bicheira/veterinária , Miíase/tratamento farmacológico , Miíase/epidemiologia , Miíase/prevenção & controle , Miíase/veterinária , ChuvaAssuntos
Doenças dos Bovinos/prevenção & controle , Infecção por Mosca da Bicheira/veterinária , Infestações por Carrapato/veterinária , Animais , Região do Caribe , Bovinos , Cooperação Internacional , Panamá , Infecção por Mosca da Bicheira/prevenção & controle , Infestações por Carrapato/prevenção & controle , Estados Unidos , United States Department of AgricultureRESUMO
Miíase é uma infestação ectoparasitária, que tem as espécies Cochliomyia hominivorax, Dermatobia hominis e Cochliomyia macellaria como maiores destaques. Os principais fatores de risco são baixo nível socioeconômico, padrões inadequados de higiene, enfermidades psiquiátricas, diabetes mellitus, imunodepressão, etilismo, desnutrição e úlcera varicosa. Os autores abordam a importância epidemiológica da miíase humana em regiões endêmicas, discorrendo sobre manifestações clínicas, diagnóstico, tratamento e medidas profiláticas...
The myiasis consists of a parasitic infestation, the species having Cochliomyia hominivorax, Dermatobia hominis and Cochliomyia macellaria as most prominent. The main risk factors are low socioeconomic status, inadequate hygiene standards, psychiatric disease, diabetes mellitus, immunosuppression, alcoholism, malnutrition and varicose ulcer. There may be asymptomatic or systemic cases with serious complications. The purpose of this article is to address the epidemiological importance of human myiasis in endemic regions, discussing clinical manifestations, diagnosis, treatment and prophylactic measures...
Assuntos
Humanos , Masculino , Feminino , Larva/parasitologia , Miíase/diagnóstico , Miíase/epidemiologia , Miíase/parasitologia , Saneamento Básico , Dor/etiologia , Ectoparasitoses/prevenção & controle , Higiene/educação , Infecção por Mosca da Bicheira/prevenção & controle , Saúde Pública , Prurido/etiologia , Fatores Socioeconômicos , Controle de Vetores de DoençasRESUMO
The economic devastation caused in the past by the New World screwworm fly Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) to the livestock industry in the U.S.A., Mexico and the rest of Central America was staggering. The eradication of this major livestock pest from North and Central America using the sterile insect technique (SIT) as part of an area-wide integrated pest management (AW-IPM) programme was a phenomenal technical and managerial accomplishment with enormous economic implications. The area is maintained screwworm-free by the weekly release of 40 million sterile flies in the Darien Gap in Panama, which prevents migration from screwworm-infested areas in Columbia. However, the species is still a major pest in many areas of the Caribbean and South America and there is considerable interest in extending the eradication programme to these countries. Understanding New World screwworm fly populations in the Caribbean and South America, which represent a continuous threat to the screwworm-free areas of Central America and the U.S.A., is a prerequisite to any future eradication campaigns. The Old World screwworm fly Chrysomya bezziana Villeneuve (Diptera: Calliphoridae) has a very wide distribution ranging from Southern Africa to Papua New Guinea and, although its economic importance is assumed to be less than that of its New World counterpart, it is a serious pest in extensive livestock production and a constant threat to pest-free areas such as Australia. In the 1980s repeated introductions and an expansion of Old World screwworm populations were reported in the Middle East; in the 1990s it invaded Iraq and since late 2007 it has been reported in Yemen, where a severe outbreak of myiasis occurred in 2008. Small-scale field trials have shown the potential of integrating the SIT in the control of this pest and various international organizations are considering using the release of sterile insects as part of an AW-IPM approach on a much wider scale. Wohlfahrtia magnifica (Schiner) (Diptera: Sarcophagidae) is a screwworm of temperate regions, which, although of limited agricultural importance, has invaded several new locations in the past few years. This special issue reports on the results of a 6-year project funded by the Joint Food and Agriculture Organization of the United Nations/International Atomic Energy Agency (FAO/IAEA) Programme of Nuclear Techniques in Food and Agriculture entitled 'Enabling Technologies for the Expansion of the SIT for Old and New World Screwworm'. A major goal of the project was to better understand population genetic variation in screwworms as an aid to the identification of isolated populations. The project also addressed issues related to genetic sexing, cuticular hydrocarbons, population dynamics, genetic transformation and chromosome analysis.
Assuntos
Infecção por Mosca da Bicheira/prevenção & controle , Infecção por Mosca da Bicheira/veterinária , Animais , Animais Domésticos/parasitologia , América Central , DNA/genética , Dípteros/patogenicidade , Feminino , Resistência a Inseticidas , Masculino , México , Infecção por Mosca da Bicheira/epidemiologia , Cromossomos Sexuais/genéticaRESUMO
New World screwworm populations in North and Central America have been the targets of virtually continuous eradication attempts by sterile insect technique (SIT) since the 1950s. Nevertheless, in some areas, such as Jamaica, SIT control programmes have failed. Reasons for the failure of SIT-based control programmes in some locations are unknown, but it has been hypothesized that failure may be related to mating incompatibility between sterile and wild fly populations or to the existence of sexually incompatible cryptic species. This paper outlines the development of a suite of four new microsatellite loci which can be used to study intra-specific relationships between populations of Cochliomyia hominivorax from the Caribbean and South America, which represent those populations involved in, or earmarked for, forthcoming SIT control. Cross-amplification with the secondary screwworm, Cochliomyia macellaria, was also successful with three of the new loci. We present results which suggest that populations from Trinidad and Jamaica form distinct groupings of flies and that C. hominivorax from Trinidad appears particularly distinct.
Assuntos
Dípteros/genética , Dípteros/patogenicidade , Repetições de Microssatélites/genética , Infecção por Mosca da Bicheira/prevenção & controle , Animais , Mapeamento Cromossômico , Primers do DNA , Ecossistema , Filogenia , Infecção por Mosca da Bicheira/epidemiologia , Infecção por Mosca da Bicheira/transmissão , América do Sul/epidemiologia , Sudeste dos Estados Unidos/epidemiologia , Clima TropicalRESUMO
Larval infestations of the New World screwworm (NWS) fly, Cochliomyia hominivorax, cause considerable economic losses through the direct mortality and reduced production of livestock. Since the 1950s, NWS populations in North and Central America have been the target of virtually continuous eradication attempts by sterile insect technique (SIT). Nevertheless, in some areas, such as Jamaica, SIT-based control programmes have failed. Reasons for the failure of SIT-based programmes in some locations are unknown, but it is hypothesized that failure may be related to the mating incompatibility between sterile and wild flies or to the existence of sexually incompatible cryptic species. Accordingly, the current research investigates intraspecific phylogenetic relationships and associated biogeographic patterns between NWS populations from the Caribbean and South America, which represent those populations involved in, or earmarked for, forthcoming SIT programmes. Uniquely, this study also includes analyses of two North American samples, collected in Texas in 1933 and 1953 prior to initiation of the SIT-based eradication programme. The study utilizes three nucleotide datasets: elongation factor-1alpha (nuclear); cytochrome oxidase subunit 1 (mitochondrial), and 12S rRNA (mitochondrial). Phylogenetic analysis of these data, representing populations from across the Caribbean, South America and Texas, indicates sub-structuring of fly populations on several of the larger Caribbean islands, suggesting a period of isolation and/or founder effects following colonization from South America; significantly, our findings do not support a North American origin for Cuban flies. The importance of these findings in the light of proposed SIT programmes in the region is discussed.
Assuntos
Dípteros/classificação , Dípteros/genética , Infecção por Mosca da Bicheira/veterinária , Animais , Cuba , DNA/genética , DNA/isolamento & purificação , Primers do DNA , República Dominicana , Ecossistema , Feminino , Efeito Fundador , Proteínas de Insetos/genética , Funções Verossimilhança , Masculino , Filogenia , Infecção por Mosca da Bicheira/epidemiologia , Infecção por Mosca da Bicheira/prevenção & controle , Alinhamento de Sequência , América do Sul/epidemiologia , Esterilização/métodos , Estados Unidos , Índias Ocidentais/epidemiologiaRESUMO
The New World screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), is one of the most important myiasis-causing flies in South America. It is responsible for severe economic losses to livestock producers, mainly because it causes mortality in newborn calves and reductions in the quality of leather and in the production of milk and meat. The economic losses caused by myiasis, along with those caused by other internal and external parasites, are the main factors limiting meat production. In Brazil, C. hominivorax has been controlled by applying insecticides, particularly organophosphate (OP)-based compounds. However, the improper and continuous use of these chemicals can lead to the selection of OP-resistant strains. This, associated with the fast development of OP resistance in other myiasis-causing flies, shows the importance of investigating resistance in C. hominivorax. Based on the findings of previous studies, the objective of the current work was to isolate and sequence the E3 gene in C. hominivorax. Mutations at the positions (Gly137 and Trp251) responsible for conferring OP resistance in Lucilia cuprina and Musca domestica L. (Muscidae) were identified in C. hominivorax. In addition, the orthologous region in C. hominivorax contained motifs that are highly conserved among carboxyl/cholinesterases and contribute to the catalytic mechanism of the active site. The characterization of this gene in natural populations of New World screwworm can be an important tool for monitoring resistance to insecticides throughout its current geographic distribution. This will provide information for the selection and implementation of more effective pest management programmes.
Assuntos
Dípteros/efeitos dos fármacos , Esterases/genética , Resistência a Inseticidas/genética , Infecção por Mosca da Bicheira/veterinária , Sequência de Aminoácidos , Animais , Bovinos , Doenças dos Bovinos/prevenção & controle , DNA Complementar/genética , Dípteros/enzimologia , Dípteros/genética , Drosophila melanogaster/genética , Feminino , Amplificação de Genes , Larva/genética , Masculino , Dados de Sequência Molecular , Infecção por Mosca da Bicheira/genética , Infecção por Mosca da Bicheira/prevenção & controle , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Esterilização/métodosRESUMO
The New World screwworm (NWS), Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), was the first insect to be effectively controlled using the sterile insect technique (SIT). Recent efforts to improve SIT control of this species have centred on the development of genetically transformed strains using the piggyBac transposon vector system. Eight transgenic strains were produced incorporating an enhanced green fluorescent protein (EGFP) marker gene under polyubiquitin regulation that has the potential for use as a genetic marking system for released males. The transgenic strains were genetically and phenotypically characterized, including for life fitness parameters and mating competitiveness. These characteristics were unique for each strain and thus some strains were deemed suitable for incorporation into SIT eradication programmes. The strain with the best attributes is designated 'CLAY'. Four of the strains, including CLAY, have been successfully cryopreserved so that their original characteristics should be unchanged when further evaluation is required. With the demonstration of efficient germ-line transformation in NWS, allowing production of fit and competitive transformants, it is now possible to consider further transgenic strain development to improve SIT that are currently being tested in other dipteran species. This includes strains that allow genetic marking with fluorescent proteins, genetic sexing by female lethality, male-specific fluorescent sorting and male sterility by testis-specific lethality. The SIT may also be improved upon by new strategies resulting in lethality of offspring of released insects using conditional lethal systems based upon temperature-dependent or dietary tetracycline regulation of lethal gene expression. Both the creation of new NWS transgenic strains and the ecological safety of their release will be enhanced by new vector systems that allow specific genomic targeting of vector constructs and their subsequent immobilization, ensuring transgene and strain stability.
Assuntos
Animais Geneticamente Modificados , Dípteros/genética , Infecção por Mosca da Bicheira/prevenção & controle , Infecção por Mosca da Bicheira/veterinária , Animais , DNA/administração & dosagem , DNA/genética , Dípteros/embriologia , Feminino , Fertilidade/genética , Regulação da Expressão Gênica , Genes Letais , Infertilidade/genética , Infertilidade/veterinária , Larva , Masculino , Microinjeções , América do Norte , Pupa , Infecção por Mosca da Bicheira/genética , América do Sul , Esterilização/métodos , Transformação GenéticaRESUMO
A field trial was carried out during a summer-fall period on a commercial beef cattle farm in Minas Gerais State, located in the Southeast of Brazil. In order to evaluate the prophylactic effect and the curative efficacy of fipronil in a 1% solution, 200 Zebu crossbred bulls, with ages varying from 20 to 30 months and weights from 233 to 362 kg, were selected. The bulls were assigned by ranked pair to an untreated control group (A) or to a treated group (B), resulting in 100 animals per group. All experimental animals were surgically castrated on day 0, following routine procedures. After castration all animals in the group B were treated with 10 mg/kg bw of a 1% fipronil solution, topically on the dorsal mid-line. The wounds were individually inspected on days: 2, 4, 7, 10, 14, 17, 21, 28 and 35. After castration the animals were naturally exposed to Cochliomyia hominivorax and remained in the same pasture throughout the trial. Among the animals in the control group, 83 were observed to harbor C. hominivorax eggs, with a total of 97 ovipositions, and among those 73 animals had active myiasis. In group B (fipronil 1%), 66 animals showed C. hominivorax eggs, with 92 ovipositions and five animals with active myiasis. Most ovipositions and active myiasis were detected until seven days post-castration for both groups. Wound parasite infestation evidenced bleeding, serous purulent exudation and presence of active C. hominivorax larvae. Treatment with fipronil 1% had a prophylactic effect on scrotal wounds against the development of C. hominivorax larvae in more than 95% of the treated animals for up to 17 days after castration. The treatment showed partial protection of 66% and 50% on days 21 and 28 post-treatment (pt), respectively. Three animals from the control group and one from the treated group showed active screwworms on day 21 pt, and one animal from the treated group and two from the control group also presented C. hominivorax larvae on scrotal wounds on day 28 pt. By the end of the observation period (day 35 pt), the castration wound had healed in all animals. All experimental animals presenting scrotal wounds infested with C. hominivorax larvae were treated with a 1% pour-on formulation of fipronil, on the same day that infestation was observed. Active C. hominivorax larvae were not seen during the monitoring period immediately after treatment. The curative efficacy of fipronil 1% against C. hominivorax larvae infestation in castration wounds was 100%.
Assuntos
Doenças dos Bovinos/parasitologia , Dípteros/crescimento & desenvolvimento , Inseticidas/uso terapêutico , Miíase/veterinária , Pirazóis/uso terapêutico , Infecção por Mosca da Bicheira/tratamento farmacológico , Infecção por Mosca da Bicheira/veterinária , Administração Tópica , Animais , Brasil , Bovinos , Doenças dos Bovinos/tratamento farmacológico , Doenças dos Bovinos/prevenção & controle , Dípteros/metabolismo , Masculino , Miíase/tratamento farmacológico , Miíase/parasitologia , Miíase/prevenção & controle , Orquiectomia/efeitos adversos , Infecção por Mosca da Bicheira/parasitologia , Infecção por Mosca da Bicheira/prevenção & controle , Escroto/parasitologia , Escroto/cirurgia , Cicatrização/efeitos dos fármacosRESUMO
The screwworm fly, Cochliomyia hominivorax (Coquerel), is a parasite that attacks all warm-blooded animals including humans. This parasite has caused significant losses to the livestock industries of the Americas. Since the screwworm eradication program was initiated in the Southeastern United States in 1957, the eradication program has successfully progressed to its current location in Panama. A variety of technologies and tools have been used in the eradication programs. The cooperative agreement has been a significant tool in the success of the program. In the United States, the State-Federal Cooperative programs provided the mechanism for carrying out screwworm eradication. Once screwworms were eradicated from the United States, the need to expand the program internationally, in order to protect the United States, became evident. A cooperative agreement created the Mexico-United States Commission for the Eradication of Screwworms (Commission). Commission-Guatemala and Commission-Belize Cooperative Agreements were used to eradicate screwworms from these countries. Followup programs in El Salvador, Honduras, Nicaragua, Costa Rica, and Panama were implemented by cooperative agreements between the United States Department of Agriculture and the individual countries. The positive and negative aspects, as well as the necessary elements of successful cooperative agreements, are discussed.
Assuntos
Dípteros , Controle de Pragas/métodos , Infecção por Mosca da Bicheira/prevenção & controle , Infecção por Mosca da Bicheira/veterinária , Criação de Animais Domésticos , Animais , América Central , Órgãos Governamentais , Humanos , Relações Interinstitucionais , Cooperação Internacional , Líbia , México , Sudeste dos Estados Unidos , Estados Unidos , United States Department of AgricultureRESUMO
Screwworm myiasis, caused by infestation of even minor wounds by the obligative parasitic larval stages of the New World screwworm (NWS) (Cochliomyia hominivorax) or Old World screwworm (OWS) (Chrysomya bezziana) flies, is a major cause of livestock morbidity and mortality in tropical and sub-tropical regions of the world. The two parasites occur in different hemispheres but are remarkably homologous. Animal health emergencies result from the invasion of new territories by the parasites or, in the case of NWS, reinfestation of areas from which the parasite had been eradicated after great effort and expense. The author reviews the biology of the parasites and the effects of screwworm, in addition to prevention of infestation upon the introduction of animals. Examples of three programmes or events are described. The first is the eradication of previously exotic NWS from an epizootic in Libya before the parasite spread to become enzootic in the Mediterranean Basin and eventually other areas of the Eastern Hemisphere. The second example reviews the serious consequences of the extension of the range of OWS into Iraq where conditions at the time were favourable for propagation and unfavourable for control. The third example describes the NWS programme strategy in North and Central America which, for forty years, has been to progressively achieve eradication and then protection of areas from north to south on that continent, employing the sterile insect technique (SIT). Outbreaks in areas where screwworm has already been eradicated divert costly programme resources and slow progress southwards, and are considered emergencies. Some problems encountered and the solutions found during the height of the eradication programme in Mexico are described. Although to date eradication of screwworms has only been accomplished with the application of SIT, this technique alone will not eradicate the pest. The author describes other elements which are required to control or eradicate screwworms. Programmes for this highly mobile parasite encompass large geographic areas and consequently require active and continuous international participation.
Assuntos
Dípteros/fisiologia , Surtos de Doenças , Infecção por Mosca da Bicheira , Animais , Surtos de Doenças/prevenção & controle , Surtos de Doenças/veterinária , Emergências/veterinária , Saúde Global , Humanos , Iraque/epidemiologia , Líbia/epidemiologia , México/epidemiologia , Controle Biológico de Vetores , Infecção por Mosca da Bicheira/epidemiologia , Infecção por Mosca da Bicheira/prevenção & controle , Infecção por Mosca da Bicheira/veterináriaRESUMO
The screw-worm Cochliomyia hominivorax (Coquerel), whose larvae develop in wild and domestic animals as well as in man, is one of the major causes of myiasis in Brazil. Sheep raising is expanding in the state of São Paulo, where information about the infestation of screw-worm is necessary for appropriate control measures. The present data were obtained from questionnaires sent to all sheep breeders belonging to Associacão Paulista de Criadores de Ovinos--ASPACO (São Paulo State Association of Sheep Breeders). Response reliability was tested by random visits paid to 10.6% of the respondents. The results show that screw-worm is the most frequent ectoparasite in the flocks and is responsible for the greatest economic losses. Its occurrence is strongly associated with flock size, reaching 100% in flocks consisting of more than 500 animals. Infestation is higher in spring and summer and lowest in the fall. The number of cases increases in the presence of some management practices such as tail amputation. Furthermore, several other associations between the indicators surveyed were also found to be significant. The data obtained will permit the elaboration of strategies for the control of this parasitosis.
Assuntos
Criação de Animais Domésticos , Infecção por Mosca da Bicheira/veterinária , Doenças dos Ovinos/epidemiologia , Fatores Etários , Amputação Cirúrgica/veterinária , Animais , Distribuição Binomial , Brasil/epidemiologia , Dípteros/crescimento & desenvolvimento , Feminino , Incidência , Masculino , Prevalência , Reprodutibilidade dos Testes , Infecção por Mosca da Bicheira/epidemiologia , Infecção por Mosca da Bicheira/prevenção & controle , Estações do Ano , Ovinos , Doenças dos Ovinos/etiologia , Doenças dos Ovinos/prevenção & controle , Inquéritos e Questionários , Cauda/cirurgia , Ferimentos e Lesões/complicações , Ferimentos e Lesões/veterináriaRESUMO
A field trial was carried out during summer 1996 in a commercial beef cattle farm located in the central area of Argentina (30 degrees 16'S, 60 degrees 30'W) to evaluate the efficacy of a new insect growth regulator material (dicyclanil) in the prevention of myiosis caused by screwworm (Cochliomyia hominivorax) larvae. Forty bull calves (Bos indicus x Bos taurus), 5 to 6 months old were allocated by ranked paris to a control (G.1) and a treated group (G.2) of the same number of animals. On day 0, all experimental animals were surgically castrated and calves of group 2 were treated topically with 20 ml as a single dose of a ready-to-use formulation containing 5% w/v dicyclanil. Inspections for screwworm larva infestation were carried out on days 4, 8, 12, 16, 19, 23 and 25 after castration. The incidence of egg masses on the scrotal wounds evidenced a similar challenge for all groups (P > 0.05 chi(2)). However, 16 animals of G.1 (80%) and only one of G.2 (5%) developed active myiosis, respectively. This difference was significant (P=0.003 X(2)).
Assuntos
Doenças dos Bovinos/prevenção & controle , Hormônios Juvenis/uso terapêutico , Orquiectomia/veterinária , Infecção por Mosca da Bicheira/veterinária , Infecção da Ferida Cirúrgica/veterinária , Administração Tópica , Animais , Argentina , Bovinos , Doenças dos Bovinos/parasitologia , Dípteros/efeitos dos fármacos , Dípteros/fisiologia , Hormônios Juvenis/administração & dosagem , Hormônios Juvenis/farmacologia , Masculino , Orquiectomia/efeitos adversos , Contagem de Ovos de Parasitas/veterinária , Infecção por Mosca da Bicheira/parasitologia , Infecção por Mosca da Bicheira/prevenção & controle , Infecção da Ferida Cirúrgica/parasitologia , Infecção da Ferida Cirúrgica/prevenção & controleRESUMO
Two studies were conducted in Brazil using induced infestations of the New World screwworm, Cochliomyia hominivorax, to investigate: a) the comparative prophylactic efficacy of doramectin and ivermectin at their recommended use levels (200 micrograms kg-1 s.c.), and b) the duration of protection of a single injection of doramectin. In the comparative efficacy study, two groups of six animals each were treated with ivermectin or doramectin. Two hours after treatment, four incisions were made. Each incision was infested with 30 first instar C. hominivorax larvae and their status evaluated daily for 7 days post-treatment (p.t.). Doramectin treatment was 100% effective in prevention of C. hominivorax infestations whereas ivermectin efficacy was incomplete. First instar larvae were eliminated in doramectin-treated calves by 48 h p.t., while in the ivermectin group, C. hominivorax developed in over 29% of the incisions. Healing began in wounds of doramectin-treated animals at 24 h p.t. and was in progress in 100% of all wounds at 2 days p.t., while 50% of ivermectin-treated calves showed incisions with active lesions. In the duration of protection study, 24 calves were allocated to six groups (T1-T6) of four animals each. Three groups (T1, T3 and T5) were treated with saline and three groups (T2, T4 and T6) with doramectin. Animals were infested as described previously according to the following schedule: T1 and T2 at day 14, T3 and T4 at day 21, and T5 and T6 at day 28 p.t. Incisions were evaluated daily for 8 days post-infestation. Screwworm infestations and viable third-instar larvae developed of all incisions of saline-treated calves, while doramectin was 100% effective preventing development of C. hominivorax for 21 days p.t. and showed partial activity at 28 days p.t.
Assuntos
Doenças dos Bovinos , Ivermectina/análogos & derivados , Ivermectina/uso terapêutico , Infecção por Mosca da Bicheira/veterinária , Animais , Brasil , Bovinos , Dípteros , Injeções Subcutâneas , Ivermectina/administração & dosagem , Masculino , Infecção por Mosca da Bicheira/prevenção & controleRESUMO
The prophylactic efficacy of ivermectin against navel or scrotal myiasis in calves was evaluated in eight trials in Argentina and Brazil. In two trials, calves were injected subcutaneously with ivermectin at a dosage of at least 200 microg kg(-1) within 24 h of birth. In the other six trials, two with two-month-old calves and four with four-month-old or older calves, all calves were treated with ivermectin at a dosage of at least 200 microg kg(-1) immediately after castration. In all trials, calves were maintained together on pasture and naturally exposed to Cochliomyia hominivorax. Navel and scrotal wounds were examined for myiasis daily for at least 14 days. Incidence of navel and scrotal myiasis was significantly lower (P < 0.01) in treated calves than in control calves.
Assuntos
Doenças dos Bovinos , Inseticidas/uso terapêutico , Ivermectina/uso terapêutico , Infecção por Mosca da Bicheira/veterinária , Animais , Animais Recém-Nascidos , Argentina , Brasil , Bovinos , Incidência , Masculino , Infecção por Mosca da Bicheira/epidemiologia , Infecção por Mosca da Bicheira/prevenção & controle , Escroto , Estações do AnoRESUMO
Three studies were conducted in Latin America--one in Venezuela, one in Argentina and one in Brazil--using a common protocol to investigate the efficacy of a single subcutaneous injection of doramectin in the prevention and control of Cochliomyia hominivorax infestations in castrated cattle. In each study, two groups of 20-28 animals each were allocated to a treated (T1) or to a control (T2) group on the basis of body weights. Animals of T1 received doramectin at 200 micrograms kg-1 (1 ml per 50 kg) and animals of T2 received saline solution at 1 ml per 50 kg of live weight. After treatment all cattle were castrated surgically. Animals were examined on treatment day and at 2, 4, 6 and 12 days post-treatment. At each observation day, the presence of C. hominivorax infestations was recorded. Doramectin was 100% effective in the prevention and control of screwworm strikes in castrated cattle exposed to continuous field infestations of C. hominivorax in tropical and subtropical areas of Latin America. Over the 12 day duration of the studies, 85%, 60% and 65% of animals in the control groups had infested wounds in Venezuela, Argentina and Brazil, respectively. Affected animals required repeated therapeutic treatment, whereas none of the doramectin-treated cattle were infested (P < 0.0001). A high proportion of the castration wounds in doramectin-treated cattle had the presence of characteristic C. hominivorax eggs but none developed into larvae. There were no clinical signs of adverse reactions to treatment in any of the three studies.
Assuntos
Doenças dos Bovinos/prevenção & controle , Inseticidas/farmacologia , Ivermectina/análogos & derivados , Infecção por Mosca da Bicheira/veterinária , Animais , Bovinos , Injeções Subcutâneas , Ivermectina/farmacologia , Masculino , Orquiectomia/veterinária , Infecção por Mosca da Bicheira/prevenção & controle , América do SulRESUMO
Two studies were conducted in Latin America, one in Venezuela and one in Argentina, using a common protocol to investigate the efficacy of a single s.c. injection of doramectin in the prevention and control of field infestations of Cochliomyia hominivorax in newborn calves and post-parturient cows. In both experiments, pregnant cows were paired on the basis of their calving time. The first cow that calved was assigned to a medicated group, and both cow and calf were treated with doramectin. The cow received a dose of 200 micrograms kg-1 and the calf 1 ml of a 1% doramectin solution. The second cow and calf were assigned to a saline-treated group, and the cow received saline at 1 ml per 50 kg and the calf 1 ml. The procedure was repeated until all animals were allocated to the two treatments. Animals were examined on the treatment day and at 2, 4, 6 and 12 days post-treatment. At each observation day, the navel of newborn calves and external genitalia of the cows were inspected and the presence of C. hominivorax infestations was recorded. Doramectin was 100% effective in the prevention and control of screwworm strikes in newborn calves and in post-parturient cows exposed to continuous field challenge of C. hominivorax. Over the 12 day duration of the studies, 48% and 57% of the saline-treated calves had screwworm navel strikes in the studies in Venezuela and Argentina, respectively. Infested animals required repeated therapeutic treatment, whereas none of the doramectin-treated calves were affected (P < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Doenças dos Bovinos/prevenção & controle , Inseticidas/uso terapêutico , Ivermectina/análogos & derivados , Infecção por Mosca da Bicheira/veterinária , Animais , Animais Recém-Nascidos , Argentina , Bovinos , Feminino , Genitália/parasitologia , Ivermectina/uso terapêutico , Infecção por Mosca da Bicheira/prevenção & controle , Umbigo/parasitologia , VenezuelaRESUMO
Two prophylactic studies and one persistent efficacy study were conducted in Brazil to evaluate one injection of doramectin at a dose rate of 200 micrograms kg-1 against induced infestations of the New World screwworm, Cochliomyia hominivorax. In each prophylactic study, 12 calves were allocated to two groups of six animals. Six calves were treated with doramectin and six with saline. Two hours after treatment, animals were anesthetized and received two incisions, one in the shoulder and one in the rump. Each incision was then infested with 50 first instar larvae. In the persistent efficacy study, 24 calves were allocated to six groups (T1-T6) of four animals each. On the day of treatment, three groups (T1, T3 and T5) were treated with saline and three groups (T2, T4 and T6) with doramectin. All animals were anesthetized and received four incisions, one in the shoulder and one in the rump of each side. Each incision was then infested with 30 first instar larvae of C. hominivorax with the following schedule: T1 and T2 at Day 3, T3 and T4 at Day 7, and T5 and T6 at Day 14 post-treatment. Calves were observed daily and incisions evaluated for 8 days post-infection. Larvae that completed development and exited the wounds were collected and incubated to evaluate viability. In all experiments, doramectin was 100% efficacious in preventing screwworm infestation caused by field isolates of C. hominivorax. First instar larvae were eliminated from the incisions of doramectin-treated calves between 24 and 48 h post-treatment, and no third instar were recovered at any time. As a consequence, healing started at 24 h and was completed at 96-120 h post-infection. Screwworm infestations and viable third-instar larvae developed in all the incisions in non-treated calves, and healing did not begin until larvae had completed their normal life cycle and exited the wounds. The persistent efficacy of a single injection of doramectin extended beyond 14 days.