Hypoderma actaeon: an emerging myiasis in roe deer (Capreolus capreolus)

Assesment of Hypoderma infestation in a wild population of Cervus elaphus from mountains Atlantic ecosystems in southwestern Europe (Spain)

Hypodermosis in Cervus elaphus was studied in the Riaño Regional Hunting Reserve, Province of León, north-western Spain. One hundred and ten red deer were examined for the presence of warble fly larvae. They were analyzed by PCR analysis of the COI region of mt-DNA and identified as Hypoderma actaeon. The prevalence of larvae was 42.7% with a mean intensity of 12.5 ± 18 (range 1-80) warbles/deer infested. The distribution of larvae in the infested animals showed an aggregated/overdispersed pattern (aggregation index = 25.84), where the larvae are not randomly or uniformly distributed, but strongly aggregated among their hosts. Larvae were found in all three states. First and second-instars were observed mainly in the autumn until the end of winter (November-March) and third-instars in late winter until mid-spring (March-May). The adult animals and the males had a higher prevalence than the young and the females, finding statistically significant differences only according to the sex of the animals. Seasonal variations were observed in the prevalence with the highest number of infested animals in winter and autumn, but not in terms of the mean intensity of parasites. Additionally, we assessed the presence of anti-Hypoderma antibodies in serum by means of indirect ELISA tests, using a crude larval extract (CLE) and a purified fraction the hypodermin C (HyC) obtained from first instars of Spanish isolates of Hypoderma lineatum (cattle). These findings confirm that H. actaeon is widely distributed in northern Spain, and provide new information about its chronobiology in mountainous Atlantic ecosystems from southwestern Europe.

Pedicle myiasis by Lucilia caesar (Diptera, Calliphoridae): An emerging disease in roe deer from north-western Spain

A total of 35 male roe deer (Capreolus capreolus) from Lugo province (north-western Spain) were examined for pedicle myiasis between 2020 and 2022. All these animals had died by different causes and were examined or preserved just after their death to avoid post-mortem infestations. After external and internal head inspection, five animals were diagnosed with severe myiasis at the basis of the antlers (14.29%; 95% confidence interval = 5.38-31.04). All the affected bucks presented a cutaneous wound (1.5-15 cm in diameter) around the pedicles with extensive tissue destruction, exposition of frontal and parietal bones, and massive infestation by dipteran larvae (2-12 mm long). Four of five roe deer showed whitish egg clusters adhered to the basis of the antlers. Moreover, in one animal, six larvae had penetrated the cranial cavity, and in two of them larvae were also found in the nasopharyngeal cavity. All the cases were recorded in summer (May-August). Morphological identification and subsequent molecular confirmation revealed that all animals were infested by different larval stages of Lucilia caesar (Diptera: Calliphoridae). This study represents the first report of pedicle myiasis in Spain. Since this disease is reported sporadically, the detection of five cases in a short period of time suggests an increase in the incidence of this myiasis.

Identification of Hypoderma actaeon (Diptera: Oestridae) in red deer (Cervus elaphus) from northern Spain: Microscopy study and molecular analysis

Hypoderma spp. larvae were observed subcutaneously in the dorsal and lumbar regions of red deer (Cervus elaphus) hunted in the province of León (northwestern Spain) causing a myiasis. They were removed and initially classified by their size, shape, color, and location under the skin into the three larval stages that parasitize these animals. The morphological characteristics of the first and second-instar are described and from the features of the third-instar the species was identified as Hypoderma actaeon. To accurately identify this species, five isolates of genomic DNA from the third-instar, two from the second-instar and two from first-instar of H. actaeon were analyzed by PCR analysis of the COI region of mt-DNA. The results confirmed that the examined samples exactly matched with H. actaeon. This study has shown the morphological identification of the three larval stages of H. actaeon and, for the first time, the first and second-instar larvae have been molecularly characterized. Finally, identification of only H. actaeon suggests that this species is the only affecting red deer in the Iberian Peninsula.

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.

First record of Pharyngomyia picta (Diptera: Oestridae) parasitizing Cervus elaphus in Sierra Nevada National Park

The necropsy made to two adult individuals of red deer shot in Sierra Nevada National Park revealed infestation by second- and third-instar larvae of the oestrid Pharyngomyia picta (Meigen 1824). The animals were shot in Dehesa de las Hoyas, about 2000 m above sea level. This is the first record of this parasite in Sierra Nevada National Park. Furthermore, the occurrence of adult P. picta at this altitude could indicate significant changes of the climatic conditions, now matching better the environmental requirements of this bot fly. Its monitoring may, therefore, be of great help for detecting global change signs.

Major differences in the larval anatomy of the digestive and excretory systems of three Oestridae species revealed by micro-CT

Oestrid flies (Diptera: Oestridae) do not feed during the adult stage, so they depend on an efficient assimilation and storage of nutrients during their parasitic larval stage. We describe the general morphology and provide volumetric data for the digestive and excretory organs of the three larval instars of the nasal bot fly Oestrus ovis L., using micro-computed tomography. The size of the digestive and excretory organs greatly increased across larval instars. In all instars, the two salivary glands were remarkably large and formed a 'glandular band' by coming together, but without lumina uniting, at their posterior ends. The distal region of the anterior Malpighian tubules was greatly enlarged and full of highly radio-opaque concretions. Moreover, the anatomy of O. ovis third-instar larva was compared to that of two species of, respectively, similar and different feeding habits: Cephenemyia stimulator (Clark) and Hypoderma actaeon Brauer. Whereas the general morphology and arrangement of the digestive and excretory systems of C. stimulator was similar to that of O. ovis, some differences were observed in H. actaeon: a swollen anterior region of the midgut, salivary glands shorter and not forming a 'band' and anterior Malpighian tubules narrowly uniform throughout their entire length.

Temporal and spatial spread of Hypoderma actaeon infection in roe deer from peninsular Spain determined by an indirect enzyme-linked immunosorbent assay

The host switching of Hypoderma actaeon (Diptera: Oestridae), a specific parasite of red deer (Cervus elaphus), towards roe deer (Capreolus capreolus) has been recently reported in Spain. To provide information about the temporal and spatial spreading of H. actaeon infection in roe deer, 244 serum samples from animals hunted in Spain between 2013 and 2018 were analysed by an indirect enzyme-linked immunosorbent assay. The overall seropositivity was 13.9%. Seropositivity was higher in continental (27.7%) and mountainous (12%) areas from central Spain, followed by southern-Mediterranean (11.2%) and northern-oceanic regions (3.5%). Differences were significant between central-continental and northern-oceanic regions (P = 0.003). No differences were found according to the sex and age of roe deer (P > 0.05). In 2013, all seropositive animals were concentrated in two distant areas in central and southern Spain, suggesting that the host switch could have occurred independently in both regions. Changes in the pattern of distribution of red deer and roe deer could have favoured the spreading of this myiasis towards roe deer, indicating that roe deer may become infested by H. actaeon in areas where both cervids coexist at high densities.

Micro-computed tomography visualization of the vestigial alimentary canal in adult oestrid flies

Oestrid flies (Diptera: Oestridae) do not feed during the adult stage as they acquire all necessary nutrients during the parasitic larval stage. The adult mouthparts and digestive tract are therefore frequently vestigial; however, morphological data on the alimentary canal in adult oestrid flies are scarce and a proper visualization of this organ system within the adult body is lacking. The present work visualizes the morphology of the alimentary canal in adults of two oestrid species, Oestrus ovis L. and Hypoderma lineatum (de Villiers), with the use of non-invasive micro-computed tomography (micro-CT) and compares it with the highly developed alimentary canal of the blow fly Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae). Both O. ovis and H. lineatum adults showed significant reductions of the cardia and the diameter of the digestive tract, an absence of the helicoidal portion of the midgut typical of other cyclorrhaphous flies, and a lack of crop and salivary glands. Given the current interest in the alimentary canal in adult dipterans in biomedical and developmental biology studies, further understanding of the morphology and development of this organ system in adult oestrids may provide valuable new insights in several areas of research.