Durably controlling bovine hypodermosis

Genome-wide phylogenetic and genetic evolutionary analyses of mitochondria in Hypoderma bovis and H. sinense on the Qinghai-Tibetan Plateau

Hypoderma bovis (H. bovis) and Hypoderma sinense (H. sinense) are insects that cause hypodermosis in yaks and Bos taurus. Hypodermosis is a severe skin condition that not only impairs the development of local animal husbandry but also poses threats to human health as a zoonosis. The Qinghai-Tibetan Plateau (QTP) is known as the "Roof of the World." Its unique geographical environment and climate conditions have supported the growth of a wide range of mammals, providing favorable conditions for Hypoderma spp. to complete their life cycles. In this study, the whole mitochondrial genomes of H. bovis and H. sinense collected from the QTP were sequenced and phylogenetically analyzed. We found that the whole genomes of H. bovis and H. sinense are 16,283 bp and 16,300 bp in length, respectively. Both the H. bovis and H. sinense genomes have 37 mitochondrial genes, which include two rRNA genes (16S rRNA and 12S rRNA), 22 tRNA genes, the control region (D-loop region), the light chain replication initiation region, and 13 protein-coding genes (PCGs). The phylogenetic tree generated based on the 13 PCGs revealed close phylogenetic relationships between H. sinense, H. bovis, and Hypoderma lineatum. A similar result was also found in our phylogenetic analysis based on 18S rRNA and 28S rRNA. However, analysis of cytochrome oxidase subunit I (COI) showed cluster of H. bovis, H. sinense, and Cuterebra spp. on the same branch, all belonging to Oestridae. The differentiation time generated based on 13 PCGs indicates that H. bovis and H. sinense differentiated and formed ~4.69 million years ago (Mya) and ~4.06 Mya, respectively. This timing coincides with the differentiation and appearance of yak and Bos taurus in the Pliocene (~4.7 Mya), indicating that the parasites and mammals diverged in close temporal proximity. Of note, this period also witnessed a rapid uplift of the QTP, causing significant climate and environmental changes. Thus, we conjecture that the differentiation of Hypoderma spp. is potentially related to the differentiation of their host species, as well as climate changes caused by the uplift of the QTP. Overall, our study can provide valuable data to support further studies on the phylogeny and differentiation of Hypoderma spp. on the QTP.

Dot-ELISA based on recombinant Hypodermin C of Przhevalskiana silenus for field diagnosis of goat warble fly infestation

Goat warble fly infestation (GWFI) is an economically important myiasis caused by larvae of Przhevalskiana silenus (Diptera, Oestridae), prevalent in countries of the Mediterranean Basin and Indian subcontinent. GWFI is characterized by the presence of subcutaneous warbles at the lumbar and sacral region of dorsum in the infested animal. The early larval instars (L1 and L2) remain inaccessible to physical detection due to their small size and subcutaneous presence thus causing hindrance in the diagnosis. The objective of present study was to develop a field applicable early diagnostic intervention for GWFI monitoring and prophylactic management for effective control of the disease. Recombinant Hypodermin C (rHyC) antigen of P. silenus was expressed in Escherichia coli. The purified protein was used for optimizing dot-ELISA in a checkerboard titration using goat warble fly infested serum as known positive. The optimized assay was further tested for lower temperature (18°C) and incubation time (30 min). The optimized assay was assessed for inter-rater reliability and field samples. The optimized conditions require 188 ng of protein/dot, 1:800 dilution of serum sample, 1:4000 dilution of anti-goat IgG conjugate and 5% skim milk powder in phosphate buffer saline as blocking buffer. The assay was found to have a diagnostic sensitivity and specificity of 97.3% and 95.8%, respectively. The inter-rater reliability of dot ELISA with rHyC indirect ELISA was found to be almost perfect with a Cohen's kappa index of 0.973. Further testing at ambient temperature (18°C) and shorter incubation steps (30 min) supported suitability of the assay for field diagnosis of GWFI. The present study provides the first report of a sensitive and specific dot-ELISA for early diagnosis of GWFI which is rapid and cost effective. The test may provide an effective field applicable tool for sustainable control of GWFI.

Epidemiological Surveillance of Hypodermosis in Cattle from Romania

Hypodermosis, or warble fly, is an endemic parasitic disease, common in countries from the northern hemisphere. The use of effective insecticides has decreased the frequency of this parasitic disease, with untreated cattle remaining to act as reservoirs. This study focused on assessing the status of hypodermosis in northwestern Romania by means of clinical examination (skin inspection and palpation performed in order to identify nodules) conducted on a number of 11.741 cattle. The study was carried out from March until June 2021. The identified larvae were subject to molecular assays for species identification and genotyping, followed by comparison with data available in the GenBank database. The average prevalence rate of parasitism caused by Hypoderma spp. was 0.31%, with values ranging from a minimum of 0.11% to a maximum of 1.32%. The dominant age group among positive animals was the 1-3 years old category and in terms of breed distribution, most positive cases were seen in cows belonging to an indigenous breed: Bruna de Maramures. April was the most prolific month in terms of nodule count/animal. The species identified in our study by means of molecular assays was H. bovis with two haplotypes: HB3 and HB8.

First report of Przhevalskiana silenus derived recombinant hypodermin C based indirect ELISA for serodiagnosis of goat warble fly myiasis

Goat warble fly infestation (GWFI) is a subcutaneous myiasis caused by larvae of Przhevalskiana silenus, an insect belonging to the order Diptera. The diagnosis of GWFI is challenging in the early larval instars (L1 and L2) as they are occult under the skin and hair coat causing prolonged economic loss in form of meat and hide damage. This necessitates early diagnosis for disease control at herd level and its prophylactic management to prevent economic losses. Hypodermins, a class of serine proteases from Hypoderminae subfamily have been used as serodiagnostic antigens for the past four decades for diagnosis of warble fly myiasis. In this study,the immunodominant antigen Hypodermin C (HyC) from P. silenus has been recombinantly expressed in E. coli and immunogenic characterisation of expressed protein was done. The protein shows hallmark residues in conserved cysteine and catalytic triad typical of serine proteases along with similar profile of immunoreactivity towards Hypoderminae infestation. The present study reports an optimised indirect-ELISA based on recombinant HyC derived from P. silenus for early diagnosis of GWFI. The optimised indirect ELISA provides a sensitive and specific immunodiagnostic for mass surveillance of the GWFI with diagnostic specificity and sensitivity of 96% and 100%, respectively and not showing any cross reactivity against other important parasitic and bacterial diseases of goats. This study presents the first report of indirect ELISA based on recombinant Hypodermin C antigen derived from P. silenus for the serosurveillance of goat warble fly disease.

Oestrid myiasis at a cross-road

The oestrids are a genuinely unique group of Diptera that represent many species whose larvae parasitize mammals, feeding on live tissues of a wide range of hosts, from mice to elephants, causing obligatory myiases. Those have had greatest impact on the activities of humans and their use of animals (e.g., as food, recreation, in the conduct of wars). To a large extent their impact has been controlled through the use of therapeutic application of synthetic chemical treatments. While in some limited cases eradication has been achieved, it is unlikely to become the norm as these parasites seem well adapted to survive at low population densities and small smoldering foci are likely to present a challenge in the future. Should organic production eschew the use of parasiticides, other than for rescue of seriously ill animals, the foci of infection by these parasites will remain. In this article, we explore current scientific information on this group of parasites that may have become an anachronism in modern livestock parasitology, identify gaps in our knowledge as well as the suggestions for the management of these parasites in the era of genomics and proteomics.

Effect of Mixed Invasions of Hypoderma bovis and Ostertagia ostertagi in Cattle on Milk Yield and Contents in Polish Dairy Farms

Wide distribution of ecto- and endoparasites in cattle is a serious problem in the sustainability of a farm, due to the negative impact on animals' health and productivity. The aim of this study was to determine the presence of antibodies against Ostertagia and Hypoderma in udder milk samples and the comparison of milk yield and content of the basic components of milk in ELISA-positive and ELISA-negative cows. Milk samples were collected from 148 lactating cows from 3 herds. Antibody detection was performed using specific ELISAs for Ostertagia ostertagi and Hypoderma bovis. Milk yield and content of protein, fat, and dry matter were studied in samples from each individual cow 11 times per year at 4 week intervals. The extensiveness of dual parasitic invasions in individual herds, estimated on the basis of udder milk testing with the ELISA test, varied and amounted to 3.22%, 11.36%, and 4.76% in the three studied herds, respectively. No antibodies were found in 61.2%, 22.7%, and 57.1% of the milk samples from the cows in each herd. The milk yield of ELISA-positive cows was significantly lower in comparison to the efficiency of ELISA-negative cows and amounted to 294 kg and even to 3672 kg of milk per year, per cow. No significant differences were found between the fat and protein contents of milk between ELISA-positive and -negative cows for both parasites.

Cytokine expression in bovine PBMC cultures stimulated with Hypoderma lineatum antigens

Hypoderma antigens are involved in host inflammation and immune response, conditioning larvae survival. In this study, peripheral blood mononuclear cell (PBMC) cultures from Hypoderma sensitized and unsensitized cattle were performed to determine the effect of H. lineatum antigens and incubation time (18, 24, 48 h) on IFN-γ, TNF-α, IL-10 and IL-4 mRNA gene expression determined by RT-qPCR. TNF-α and IL-4 gene expression were higher in Hypoderma previously sensitized PBMCs, suggesting that a mixed Th1/Th2 response may play a significant role in host defence reactions against Hypoderma exhibited by previously infested cattle. Incubation time had a significant effect on IL-10 and TNF-α gene expression, which decreased over time. Regarding to H. lineatum antigens, the crude larval extract and the purified fraction hypodermin B (HB) produced a significant reduction of the mRNA expression levels of the proinflammatory cytokine, IFN-γ; moreover, the HB had a stimulating effect on the mRNA gene expression of the anti-inflammatory cytokine IL-10, demonstrating that the parasite would modulate the host defence mechanisms by avoiding harmful immune responses that would limit its survival into the host tissues.

The family Oestridae in Egypt and Saudi Arabia (Diptera, Oestroidea)

All known taxa of the family Oestridae (superfamily Oestroidea) in both Egypt and Saudi Arabia are systematically catalogued herein. Three oestrid subfamilies have been recorded in Saudi Arabia and/or Egypt by six genera: Gasterophilus (Gasterophilinae), Hypoderma, Przhevalskiana (Hypodermatinae), Cephalopina, Oestrus, and Rhinoestrus (Oestrinae). Five Gasterophilus spp. have been recorded in Egypt, namely, G. haemorrhoidalis (Linnaeus), G. intestinalis (De Geer), G. nasalis (Linnaeus), G. nigricornis (Loew), and G. pecorum (Fabricius). Only two of these species have also been recorded in Saudi Arabia, namely: G. intestinalis (De Geer) and G. nasalis (Linnaeus). The subfamily Hypodermatinae is represented in the two countries by only four species in two genera, namely, H. bovis (Linnaeus) and H. desertorum Brauer (in Egypt only), and H. lineatum (Villers) (in Saudi Arabia only) and Przhevalskiana silenus (Brauer) (in both countries). The subfamily Oestrinae is represented by two widely distributed species in both countries, namely, C. titillator (Clark) and O. ovis (L.), in addition to another species represented in Egypt only, R. purpureus (Brauer). For each species, synonymies, type localities, distribution, Egyptian and Saudi Arabian localities with coordinates, and collection dates are presented.

LONGRANGE® (eprinomectin 5% w/v extended-release injection) efficacy against Hypoderma lineatum in an endemic area in southern Italy

Background

Despite intensive control measures including governmental campaigns using highly-efficacious systemic insecticides, there is evidence for persisting or recurring bovine Hypoderma species populations in parts of Europe, the USA and Canada. The present study evaluated the efficacy of LONGRANGE® (eprinomectin 5% w/v extended-release injection) against the infestation of cattle with Hypoderma lineatum, which is considered to be the predominant bovine warble fly in southern Europe and in North America.

Methods

Thirty-six local breed cattle sourced in an endemic area in southern Italy and confirmed positive for Hypoderma exposure by ELISA were randomly assigned to three groups of 12 animals each. Cattle of one group served as control and received saline injectable solution, whereas those in the two other groups received LONGRANGE® by subcutaneous injection. LONGRANGE® was administered once, either when Hypoderma larvae were expected to be first-instars (L1) or after warbles development, with Hypoderma larvae moulting to the second-(L2) and third-(L3) instars. Cattle were checked at intervals for warbles and Hypoderma larvae were collected, examined for their viability and morphologically identified. The detection of Hypoderma on cattle was terminated when warbles were no longer emerging.

Results

All intact larvae collected were identified as H. lineatum. No live larvae were collected from any animal treated with LONGRANGE® while live specimens were sampled from nine of the 12 control cattle (1 to 9 larvae per animal) (P = 0.0001 at α = 0.05). LONGRANGE® treatment was well accepted and no adverse events related to treatment or other health problems were observed.

Conclusions

This study confirmed the continued ‘preventive’ (efficacy against migrating L1) and ‘therapeutic’ (efficacy against L2 and L3 in warbles) efficacy of LONGRANGE® against H. lineatum infestation of cattle under contemporary field conditions.

First Molecular Characterization of Hypoderma actaeon in Cattle and Red Deer (Cervus elaphus) in Portugal

Hypoderma spp. larvae cause subcutaneous myiasis in several animal species. The objective of the present investigation was to identify and characterize morphologically and molecularly the larvae of Hypoderma spp. collected from cattle (Bos taurus taurus) and red deer (Cervus elaphus) in the district of Castelo Branco, Portugal. For this purpose, a total of 8 larvae were collected from cattle (n=2) and red deer (n=6). After morphological identification of Hypoderma spp. larvae, molecular characterization was based on PCR-RFLP and mitochondrial CO1 gene sequence analysis. All larvae were morphologically characterized as the third instar larvae (L3) of H. actaeon. Two restriction enzymes were used for molecular identification of the larvae. TaqI restriction enzyme was not able to cut H. actaeon. However, MboII restriction enzyme differentiated Hypoderma species showing 210 and 450 bp bands in H. actaeon. Furthermore, according to the alignment of the mt-CO1 gene sequences of Hypoderma species and to PCR-RFLP findings, all the identified Hypoderma larvae were confirmed as H. actaeon. This is the first report of identification of Hypoderma spp. (Diptera; Oestridae) from cattle and red deer in Portugal, based on morphological and molecular analyses.

Molecular Characterization of Hypoderma SPP. in Domestic Ruminants from Turkey and Pakistan

The aim of this study was to determine the morphological and molecular characterization of Hypoderma spp. in cattle and yak from provinces in Turkey and Pakistan. In total, 78 Hypoderma larvae were collected from slaughtered animals in Turkey and Pakistan from October 2015 to January 2016. Thirty-eight of these 78 Hypoderma larvae were morphologically classified as third instar larvae (L3s) of Hypoderma bovis, 37 were classified as Hypoderma lineatum, and 3 were classified as suspected or unidentified. The restriction enzyme TaqI was used to differentiate the Hypoderma spp. by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). According to the sequences and the PCR-RFLP results, all larval samples from cattle from Turkey were classified as H. bovis, except for 1 sample classified as H. lineatum. All Hypoderma larvae from Pakistan were classified as H. lineatum from cattle and as Hypoderma sinense from yak. This study provides the first molecular characterization of H. lineatum (cattle) and H. sinense (yak) in Pakistan based on PCR-RFLP and sequencing results.

Treatment and control of bovine hypodermosis with ivermectin long-acting injection (IVOMEC® GOLD)

Background

The studies reported here were conducted to assess the efficacy of ivermectin long-acting injection (IVM LAI; IVOMEC® GOLD, Merial; 3.15 % w/v ivermectin) for the treatment and control of natural infestations of cattle by Hypoderma bovis and Hypoderma lineatum, which are the most economically important oestrid flies of cattle in the northern hemisphere.

Methods

Cattle selected from herds with a history of Hypoderma infestation were grouped into blocks of three (Italy, 33 cattle; Germany, 30 cattle) or two (USA, 16 cattle) animals each, on the basis of positivity at the pre-treatment anti-Hypoderma antibody titres. Within each block, animals were randomly allocated to one of the following treatment regimens: saline (control); IVM LAI, administered at the predicted time of occurrence of first-instar larvae (Italy, Germany, USA); IVM LAI, administered at the predicted time of occurrence of second- and/or third-instar larvae (Italy, Germany). All treatments were administered by subcutaneous injection in correspondence of the area anterior to the shoulder at 1 ml/50 kg body weight, which corresponds to 630 mcg IVM/kg for IVM LAI.

Results

No Hypoderma larvae emerged from animals treated with IVM LAI, whereas live H. lineatum (Italy) or H. bovis (Germany, USA) larvae were collected from saline-treated animals (P < 0.01). No adverse reactions to treatments were in any of the animals enrolled in the study.

Conclusions

The results from this study demonstrate that ivermectin in a long-acting formulation is 100 % efficacious in the treatment of cattle naturally infested by H. bovis and H. lineatum larvae at all stages of development. IVM LAI can, therefore, be used as ‘prophylactic’ treatment for Hypoderma spp. infestations in absence of external evidence of their presence and thus prior to skin and carcass damage, and as ‘therapeutic’ treatment, when warbles are already present.

An overview on different aspects of hypodermosis: Current status and future prospects

Livestock plays a vital role in economic development of a nation and is being used in agriculture for draft power, production of farmyard manure as well as milk and meat production. Bovine hypodermosis is the top culprit among all parasitic infections across the world. Hypodermosis is an endemic disease in the mountainous areas/plain areas and is regularly observed in the northern hemisphere of the globe affecting cattle, deer, yaks and buffaloes. There is a wide variation in geographical distribution of Hypoderma spp. during the years 1945-2015. The manuscript includes a geospatial study that tries to maps the global distribution of hypodermosis in different areas of the world in order to detect hotspots or endemic areas that may be a potential source for disease spread. This information's are very useful to predict the potential high risk areas that are prone to disease outbreak. The present review aims to evaluate the global distribution, molecular discrimination, diagnostics and vaccination of hypodermosis, focusing on its current status and future perspectives towards the management of the disease and its control strategies.

Genetic diversity and population genetics of the warble flies Hypoderma bovis and H. sinense in Qinghai Province, China

BACKGROUND

Hypoderma bovis and H. sinense (Diptera: Oestridae) mainly parasitise cattle and yaks. The two parasites are pathogenic and cause economic losses that result from reduced amounts of livestock products, including milk, meat, and skin. Genetic diversity and population genetic structure of H. bovis and H. sinense have not been evaluated, but could be used to inform appropriate strategies to control these parasites.

METHODS

We cloned and sequenced part of the mitochondrial cytochrome c oxidase subunit I (COI) gene from 60 H. bovis isolates and 52 H. sinense isolates from five locations in Qinghai Province, China, to identify polymorphisms, and infer their phylogenetic relationships, historical population expansions, and divergence time.

RESULTS

We identified 17 COI haplotypes from the H. bovis samples, and 23 COI haplotypes from the H. sinense samples. The haplotype and nucleotide diversities were 0.738 and 0.00202 for H. bovis, and 0.867 and 0.00300 for H. sinense, respectively, which indicates rich genetic diversity in H. bovis and H. sinense populations. Bayesian phylogenetic analysis revealed that the two species are monophyletic, and geographical structuring of haplotypes was significantly different in H. sinense (P < 0.05), but not H. bovis. Neutrality tests and mismatch distribution statistical analysis revealed that populations of the two species have undergone demographic expansions. The divergence three Hypoderma spp. (H. bovis, H. lineatum, and H. sinense) was estimated to have occurred approximately 4.5 million years ago (Mya), which indicates that the rapid uplift of the Qinghai-Tibetan Plateau during the late Miocene-Pliocene was associated with divergence of Hypoderma species.

CONCLUSIONS

Results of the present study revealed that both H. bovis and H. sinense displayed high genetic diversity and widespread population genetic differentiation within and among populations; these data, along with the molecular phylogeny, demographic history, and divergence time estimation, provide new insight into evolutionary history of these species. These findings will help elucidate speciation in Hypoderma and provide theoretical basis for epidemiological surveillance and control of these species on the Qinghai-Tibetan Plateau.

The immunobiology of myiasis infections--whatever happened to vaccination?

The current state of myiasis vaccine technologies are reviewed mainly in the primary research genera of Lucilia and Hypoderma. The importance of myiasis flies as primary causes of morbidity and mortality in agricultural species and man has not diminished despite the existence of good control strategies. However, the development of vaccines against myiasis infections has been relatively quiescent for more than 10 years despite the rapid development of genomic and proteomic analysis and of skills in data interpretation. The value of vaccine research in an era of chemical primacy is analysed. In fact, recent findings of drug resistance and the impact of animal welfare concerns should mean a renewed interest in alternative controls. The reasons that this has not been true to date are explored and new possibilities discussed.

An epidemiological study of Hypoderma infection and control using ivermectin in yaks in Qinghai Province, China

The prevalence of Hypoderma spp. in yaks grazed in the east of Qinghai province was investigated in 2008. In this area, the prevalence in young yaks (1- to 3-year-old) was very high at 82.2–98.7%, whilst in adult yaks (4-year-old and older), the prevalence was 42.4–50.6%. The seasonal development and migration pattern of Hypoderma larvae in yak bodies was found to be similar for different locations in this area. The numbers of first, second and third instar larvae detected in yak bodies peaked in October, December and March, respectively. Different doses of ivermectin (125 to 500 µg/kg body weight) almost completely dewormed the larvae from yaks, suggesting that using a quarter of the prescribed dose (500 µg/kg body weight) was effective. In October of each year between 2009 and 2012, ivermectin (125 µg/kg body weight) was administered to a total of 562,995 yaks grazed in four counties in Qinghai province, and the pevalence of Hypoderma larval infection in yaks was reduced to 0.5–1.0%.

The presence of anti-Hypoderma antibodies in udder milk samples, and correlation with selected parameters of dairy performance

Hypodermosis is responsible for significant economic losses and remains a current problem in animal husbandry. This study determined the extent of Hypoderma spp. invasion in north-eastern Poland in dairy herds. The extent of the invasion, determined on the basis of positive results of an ELISA assay (Bovine Hypodermosis Milk Screening of Institut Pourquier), varied in herds. Statistical analysis performed on the results of milk productivity and content of basic components revealed a decrease in the milk yield and changes in milk protein in animals revealing positive, doubtful and negative results. Statistically significant differences were absent as regards the content of milk fat or milk total solids. The milk yield and the content of particular milk components were determined using the AT4 method, as part of a control program carried out by the Polish Federation of Cattle Breeders and Dairy Farmers (PFHBiPM).

A serological and molecular survey of cattle hypodermosis in east-Turkey

The aim of this study was to determine the seroprevalence of hypodermosis in cattle in East-Turkey and to identify Hypoderma species using morphological and molecular methods. For this purpose, a total of 778 serum samples of cattle were collected from Erzurum provinces of east-Turkey from December 2008 to February 2009. The sera were analyzed using a Hypodermin C antigen by means of indirect ELISA. In addition, 10 Hypoderma spp. larvae were collected from slaughtered animals in the abattoir for morphological identification and molecular characterization on the basis of mitochondrial CO1 gene sequence analysis and PCR-RFLP. Two hundred and twenty three (28.6%) out of 778 cattle were seropositive for hypoderma antibodies. All positive cattle were female of a local breed. Seven out of 10 Hypoderma larvae were morphologically classified as third instar larvae (L3) of H. bovis and 3 were classified as L3 of H. lineatum. The TaqI restriction enzyme was used to differentiate the Hypoderma species on the basis of the 438 and 250 bp bands for H. bovis and the 488 and 200 bp bands for H. lineatum resulting from PCR-RFLP. According to the alignment of the mitochondrial CO1 sequences of the Hypoderma species and the PCR-RFLP results, all examined larva samples were classified as H. bovis.

Bovine hypodermosis--a global aspect

Cattle hypodermosis (warble fly infestation) is a notorious veterinary problem throughout the world. Larvae of Hypoderma species cause a subcutaneous myiasis of domesticated and wild ruminants. This disease is caused by, Hypoderma bovis, Hypoderma lineatum in cattle whereas, Hypoderma diana, Hypoderma actaeon, and Hypoderma tarandi, affect roe deer, red deer, and reindeer, respectively. Adults of the cattle grub are commonly known as heel flies, warble flies, bomb flies or gad flies. The biology of hypodermosis is complex because it passes through ecto- as well as endoparasitic stages in the life cycle. The parasitic stage of hypodermosis lasts about 1 year in domesticated as well as in the wild animals, while in the adult stage, a free-living fly lasts only for few days. The diagnosis of hypodermosis is of prime importance for planning treatment and the eradication program. Generally, there are two methods that are routinely used for diagnosis of hypodermosis, i.e., the direct clinical examination and immuno diagnosis by the use of pooled serum and/or milk sample. For the control of hypodermosis, different preparations are available and their use in most of the countries is limited to an individual level but never cover the whole cattle population of a country. Re-infestation in the herd occurs due to the untreated animals that remain the reservoir of the disease. The disease causes huge economic losses in animal production due to the effect of this disease on meat, milk, and the leather industry. It can also affect the general health status as well as the immune system of the body of the diseased animals. As regards the control measures of the disease, different methods have been efficiently practiced and consequently this disease is controlled at national level in many European countries.

Cutaneous myiasis

Myiasis is the infestation of living tissue by the larvae of flies in the order Diptera. Cutaneous involvement is the most common type of myiasis. Cutaneous myiasis can be subdivided into furuncular, migratory, and wound myiasis. Each subtype is reviewed with discussion of the larvae involved, presenting signs and symptoms, clinical differential diagnoses, and treatment. Preventive measures are also described.

LEARNING OBJECTIVES

At the conclusion of this learning activity, participants should be familiar with the causal agents, clinical manifestations, and treatment of human cutaneous myiasis.

Seroprevalence of hypodermosis in cattle in some provinces of Turkey

The aim of this study was to determine the seroprevalence of hypodermosis in cattle in the east and southeast of Turkey. For this purpose, a total of 634 sera samples of cattle were collected from Malatya, Elazig and Diyarbakir provinces of east and southeast of Turkey from November 2005 to February 2006. The sera were analyzed using a Hypodermin C antigen by means of indirect ELISA. One hundred and forty eight (23.3%) out of 634 cattle were seropositive for hypoderma antibodies. The highest percentage of seropositivity were detected at Elazig province (26.3%) followed by Malatya (22.3%) and Diyarbakir provinces (22.1%). The seropositivity rate was higher in female (31%) than male (14.1%). When the mean is considered by animal breed, the highest seropositivity was detected at local breed (27.7%) following crossbreed (26.8%) and purebreed (19.7%). There was a positive relation between age and seropositivity. Seropositivity rate was 15.9% in 2 and under ages while these rates were 38.1% and 30.4% in 3-4 ages and 5 and up ages, respectively.

Cross-transmission studies with Hypoderma lineatum de Vill. (Diptera: Oestridae): attempted infestation of goats (Capra hircus)

The potential for cross-transmission of Hypoderma lineatum from cattle to domestic goats (Capra hircus) was examined using artificial infestation techniques. Two routes of infestation, subcutaneous injection and dermal penetration, were used to expose goats to newly hatched first instars. Presence of antibodies and appearance of circulating antigen (hypodermin C) were evaluated at selected intervals for up to 40 weeks post-infestation. In addition, immunoblots against H. lineatum first-instar proteins were conducted using sera taken at 10 weeks post-infestation. Goats were palpated for the presence of developing larvae at sub-dermal sites beginning at week 30 pi. No developing larvae were palpated at any time, regardless of the route of infestation nor was circulating antigen detected in any infested goats. Antibodies were present at weeks 6 and 10 and week 27 pi in both infested groups. Immunoblots indicated all infested goats produced antibodies to first instar H. lineatum antigens. H. lineatum appears to be incapable of completing development in domestic goats although the transient appearance of ELISA detectable antibodies and the presence of bands on immunoblots suggests that at least some larvae survive long-enough to engender a humoural response. The host specificity of H. lineatum is discussed in light of the general concepts of host-parasite relationships of oestrids.

Successful and currently ongoing parasite eradication programs

The eradication of parasitic diseases is not a new concept. The most successful programs of parasite eradication have occurred with species of veterinary importance. The first such program, the eradication of Texas Cattle Fever from the United States, is one of the great success stories of disease eradication. The American screwworm eradication program is ongoing and is serving as a guiding impetus for many of the ongoing or proposed vector eradication schemes around the world. The success of these programs prompted similar successful operations in human health. Although they once led the way, veterinary parasitologists have taken second place in eradication planning. The only three parasitic diseases of veterinary importance that have been targets of recent eradication programs are Hypoderma species in Great Britain and Europe, Cochliomyia hominivorax after its introduction into Libya from the Americas, and Echinococcus granulosus in Tasmania, Australia. There is also work on the eradication of the tick, Amblyomma variegatum, from the Caribbean Islands. Some animal diseases are targeted under the auspices of the human eradication programs, most notably the eradication of the tsetse fly from parts or all of Africa. This paper reviews some of the past or ongoing successful eradication programs and presents a brief summary of the history of the programs, the methods used or planned, and potential controversies surrounding their success and implementation.

Human and livestock migrations: a history of bot fly biodiversity in the Mediterranean region

The bot fly (oestrid) is responsible for myiasis in domestic animals. The presence in some regions of southern Europe of an unusually large number of different species of bot fly suggests a high degree of oestrid biodiversity in this area. The many factors that can influence parasitic species composition (e.g. host and parasite genetics, relationships with their hosts and environment, and animal management) include the movement of domestic animals in association with migrating human populations in southern Europe over thousands of years. From its geographical position, which was strategically important in controlling commercial trade routes in early Western civilization, the Mediterranean sea has for more than 3000 years constituted the hub of many different cultures, populations, genes and agricultural practices. The movement of animals and their associated parasites in this region can help to explain the evolution of parasitic biodiversity.

Efficacy of moxidectin injectable and pour-on formulations in a pilot control program against bovine hypodermosis in Southern Italy

Bovine hypodermosis is a myiasis caused by Hypoderma bovis and Hypoderma lineatum (Diptera, Oestridae) larvae, which has a severe economic impact on the livestock industry. Though myiasis is widespread throughout Italy, no nationwide eradication program has ever been planned, unlike in other European Countries. With a view to setting up a national control program, a pilot study was carried out in Southern Italy on 9939 cattle bred in an area with a high prevalence of cattle hypodermosis, using moxidectin 0.5% pour-on (Cydectin, Fort Dodge) and 1% injectable (Cydectin, Fort Dodge) formulations. At the recommended dosage, moxidectin displayed efficacy levels of 99.9% in the pour-on and 100% in the injectable formulation, whereas the microdose (1 mg per head regardless of body weight) was less effective (65.7%). This trial contributed to a significant reduction in infestation rates in the study area and represented the first step through which a national program for eradicating warble fly infestation in Italy.

Sero-epidemiological surveillance of hypodermosis in yaks and cattle in north China by ELISA

A large-scale serological surveillance was conducted for hypodermosis in the north of China. A total of 4175 sera samples of yaks and cattle were collected from five provinces in north China that included Xinjiang, Inner Mongolia, Heilongjiang, Jiling and Gansu provinces, between 2001 and 2002, and were examined for anti-hypoderma antibody by ELISA. The results indicate that the naturally infested positive rates of Hypoderma spp. in the above provinces were 51.77%, 27.02%, 13.00%, 6.03% and 44.41%, respectively. These results suggest a significant warble fly population in the north of China. Positive sera were collected from infested cattle in Pingliang county of the Gansu province monthly between August 2001 and July 2002. These sera were used to evaluate the seasonal kinetics of anti-hypoderma antibody. The kinetics demonstrated that anti-hypoderma antibody was elevated from October to December. Thus, serological surveillances associated with low infestation rates and chemical therapy would best be performed from October to December in the region.

Cattle grub infestation by Hypoderma sp. in Albania and risks for European countries

In order to estimate the presence and the seroprevalence of hypodermosis in Albania, 625 head of cattle were bled during two sampling seasons (i.e. from February to March 2003 and from November to December 2003). The cattle came from three collection sites in Northern (site A), Central (site B) and Southern (site C) Albania. Milk samples were collected monthly from four animals from October 2002 to May 2003 during the lactating period. The animals were also clinically examined for the presence of warbles by manual palpation from April to July 2003 and 2004 and third instar larvae were collected and morphologically identified. Serum and milk samples were processed by ELISA. One hundred and thirty-three (38.6%) out of 344 and 116 (41.3%) out of 281 animals were found to be seropositive for Hypoderma during the first and the second sampling season. In particular, the animals from site C presented the highest percentage of seropositive results (i.e. 72.8% and 97.8% in the first and in second year, respectively) followed by the animals from sites A (i.e. 35.8% and 23.8% in the first and in second year, respectively) and B (i.e. 17.8% and 3.4% in the first and in second year, respectively). The kinetics of anti-Hypoderma antibodies in milk samples showed the highest antibody titres from October to February 2003. All the seropositive animals in both the sampling periods showed the presence of one or more warbles under the skin during April and May 2003 and 2004 and the third-stage larvae collected were morphologically identified as Hypoderma bovis. The results of this survey indicate that hypodermosis is widespread in Albania and that early prophylactic treatments must be carried out accordingly. The hope is not only to reduce the parasitic intensity with obvious benefits for livestock production, but also to avoid the risk of spreading this parasitic disease to neighboring countries.

A THIRD SPECIES OF HYPODERMA (DIPTERA: OESTRIDAE) AFFECTING CATTLE AND YAKS IN CHINA: MOLECULAR AND MORPHOLOGICAL EVIDENCE

Cattle and yak hypodermosis in China is caused by Hypoderma bovis and H. lineatum, with a prevalence reaching up to 98-100% of the animals and maximum intensities exceeding 400 warbles for each animal. A third species, H. sinense, is also considered by Chinese researchers to affect livestock. The molecular characterization of the most variable region of the mitochondrial cytochrome oxidase I gene and of the ribosomal 28S gene has been performed for the third-stage larvae collected from cattle and yaks in China and identified (on the basis of the spinulation on the ventral side of the 10th segment) as H. bovis, H. lineatum, and H. sinense. Amplicons were digested with the HinfI and BfaI restriction enzymes, which provided diagnostic profiles to simultaneously differentiate the 3 Hypoderma species. Third-stage larvae of H. sinense were also examined by scanning electron microscopy, which revealed proper morphological characteristics different from those of H. bovis and H. lineatum. The molecular and morphological evidence herein reported support the existence of a third species of Hypoderma affecting cattle and yaks in China, and the results provide new tools for unequivocal identification of this species and present key components for the evaluation of its endogenous cycle and pathogenicity in animals and humans.

Migration of warble fly larvae in the yak and optimum timing of ivermectin treatment

Sixty yaks were autopsied to determine the migration pattern of warble fly larvae. In August, first instars were observed in the body of yak for the first time. These larvae peaked in number in October. From November to February, second instars were detected and their number peaked in January. Third instars appeared in January and peaked in March. Forty-five yaks were administered with ivermectin: 15 animals in September, 15 in October and 15 in November. Between December and June, the number of warbles was checked by palpation. Although some warbles were observed in the September- and November-treated groups, no warbles were detected in the October-treated group. Treatment of yaks with ivermectin was most effective for warble fly in October.

Parelaphostrongylus tenuis and other parasitic diseases of the ruminant nervous system

There are many parasites that affect the ruminant central nervous system. Clinical signs can vary dramatically based on the location and mobility of the parasite. Clinical disease can occur due to the physical presence of the parasite and the resulting host immune response or the toxin produced by the parasite. Differentiating the cause of disease is particularly important because prognosis,treatment, and subsequent control measures vary dramatically depending on the disease process. This article focuses on the pathogenesis,treatment, and control of some of the more common parasitic diseases of the ruminant central nervous system.

Uptake of bovine IgG by first instars of the common cattle grub, Hypoderma lineatum

The midgut of first instar Hypoderma lineatum (De Vill.) (Diptera: Oestridae) was examined for the presence of bovine immunoglobulin using immuno-gold staining in conjunction with image analysis. Newly hatched larvae, unexposed to fluids or tissues of the host, showed little or no deposit of colloidal gold particles. Midgut lumen, microvillar border, epithelial cell bodies and basement membrane of first instars, 6-7 months of age, recovered from the host oesophagus, all showed colloidal gold staining. This indicates that immuno-reactive portions of bovine immunoglobulin survive exposure to extracorporeal larval enzymes, as well as transit of the midgut, and pass through epithelial cells to enter the larval haemocoel.

Efficacy of injectable and pour-on microdose ivermectin in the treatment of goat warble fly infestation by Przhevalskiana silenus (Diptera, Oestridae)

The prophylactic efficacy of microdoses of injectable and pour-on ivermectin formulations against larval stages of Przhevalskiana silenus was assessed in naturally infected goats in the region of Calabria (southern Italy).Sixty-eight goats from two goat farms were divided into five groups: one group remained untreated, while the other four groups were treated with microdoses of ivermectin (5 and 10 microg/kg injectable formulation and 10 and 20 microg/kg pour-on formulation). The microdoses of ivermectin were fully effective in the treatment of goat warble fly infestation (GWFI) as no larvae emerged from the warbles in the treated groups, while all the larvae emerged in the control groups. Irrespective of the type of formulation used, the difference between the treated groups and the control group was statistically significant (P< 0.001). By contrast, no statistical differences were found between the goats treated with the injectable formulation and those receiving the pour-on applications, and between the two doses of the injectable and pour-on formulations used. Given the plasma concentrations it attains at its lowest dose (0.052 - 0.042 ng/ml for the injectable formulation and 0.030 ng/ml for the pour-on) the injectable formulation seems to offer the most reliable route for the administration of ivermectin microdoses and it is acceptable for milk consumption. The introduction of ivermectin in the early eighties and the use of microdoses in some cases have made it possible to control cattle hypodermosis in large areas of Europe. As with cattle hypodermosis, the administration of ivermectin microdoses in goats is particularly interesting because of the low costs involved and the low levels of residues found in goat milk; it may thus constitute the basis for GWFI control campaigns in areas where the disease is prevalent.