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1.
Med Vet Entomol ; 32(3): 323-333, 2018 09.
Article in English | MEDLINE | ID: mdl-29658151

ABSTRACT

The Old World screwworm fly (OWSF), Chrysomya bezziana (Diptera: Calliphoridae), is an important agent of traumatic myiasis and, as such, a major human and animal health problem. In the implementation of OWSF control operations, it is important to determine the geographical origins of such disease-causing species in order to establish whether they derive from endemic or invading populations. Gross morphological and molecular studies have demonstrated the existence of two distinct lineages of this species, one African and the other Asian. Wing morphometry is known to be of substantial assistance in identifying the geographical origin of individuals because it provides diagnostic markers that complement molecular diagnostics. However, placement of the landmarks used in traditional geometric morphometric analysis can be time-consuming and subject to error caused by operator subjectivity. Here we report results of an image-based approach to geometric morphometric analysis for delivering wing-based identifications. Our results indicate that this approach can produce identifications that are practically indistinguishable from more traditional landmark-based results. In addition, we demonstrate that the direct analysis of digital wing images can be used to discriminate between three Chrysomya species of veterinary and forensic importance and between C. bezziana genders.


Subject(s)
Diagnosis, Computer-Assisted/veterinary , Diptera/classification , Screw Worm Infection/diagnosis , Wings, Animal/anatomy & histology , Animals , Diagnosis, Computer-Assisted/methods , Diptera/anatomy & histology , Female , Male , Screw Worm Infection/parasitology
2.
Aust Vet J ; 95(8): 265-272, 2017 Aug.
Article in English | MEDLINE | ID: mdl-28749021

ABSTRACT

OBJECTIVE: To determine the prophylactic and therapeutic efficacy of Australian-registered insecticide formulations against Old World screwworm (OWS) myiases for potential use in screwworm containment and eradication programs. METHODS: The longevity of protection provided by six insecticidal formulations (subcutaneous ivermectin, doramectin and abamectin, a topically applied aqueous formulation of spinosad, ivermectin controlled-release capsule and a dicyclanil spray-on formulation) was tested using implants of 1st-instar OWS larvae on Javanese thin-tail sheep. Therapeutic efficacy of four formulations (topical ivermectin, chlorfenvinphos/cypermethrin mixture, aerosol spinosad formulation and a formulation containing propetamphos and eucalyptus oil) was tested against 2- and 4-day-old OWS strikes. RESULTS: Both the ivermectin capsule and dicyclanil spray-on formulation gave 100% protection against screwworm implants for the full 12 weeks of the study. Ivermectin, doramectin and abamectin administered SC all gave 100% protection at 3 days post-treatment, but at 2 weeks the protection had become incomplete. Spinosad dipping did not give complete protection at any time. All four therapeutic treatments gave complete resolution of 2-day-old strikes and topical ivermectin, spinosad and chlorfenvinphos/cypermethrin, but not the propetamphos/eucalyptus oil formulation, gave complete resolution of all 4-day-old strikes. CONCLUSION: Dicyclanil spray-on and ivermectin capsule formulations, both registered for use in sheep, but not for cattle or other livestock species, gave much longer protection against screwworm implants than the currently recommended SC ivermectin. Pre-emptive action to facilitate rapid deployment of these formulations in the event of a screwworm incursion is urgently needed.


Subject(s)
Insecticides/therapeutic use , Ivermectin/therapeutic use , Screw Worm Infection/veterinary , Sheep Diseases/drug therapy , Sheep Diseases/prevention & control , Animals , Australia , Diptera , Indonesia , Screw Worm Infection/drug therapy , Screw Worm Infection/prevention & control , Sheep
3.
Acta Trop ; 138 Suppl: S42-8, 2014 Oct.
Article in English | MEDLINE | ID: mdl-25016294

ABSTRACT

A new protocol was developed to overcome obstacles to the high-throughput sequence analysis of the 716-717 nucleotides at the carboxyl terminal of the mitochondrial gene cytochrome b (cyt b) of the myiasis flies Chrysomya bezziana and Wohlfahrtia magnifica. For both of these obligate parasites, cyt b haplotypes provide diagnostic markers for phylogeographic populations, markers that identify the origins of emerging populations causing economically important myiasis in livestock and, in the case of C. bezziana (Old World screwworm fly), could help select reproductively-compatible populations for use in the Sterile insect technique as part of area wide integrated pest management. High sequence quality is important for unambiguously detecting the few mutations that are diagnostic for regional cyt b haplotypes and their lineages. A key innovation is the design of a new forward primer for the specific PCR amplification and high-quality sequencing of cyt b. The improved protocol will facilitate the use of this established comparative cyt b sequence analysis, not only by teams lacking the resources for whole genome sequencing (WGS) but also by those requiring reference sequences for developing comparative mitogenomics based on WGS.


Subject(s)
Cytochromes b/genetics , DNA, Mitochondrial/genetics , Diptera/classification , Diptera/genetics , Phylogeography , Polymerase Chain Reaction/methods , Animals , Entomology/methods , Genetic Testing/methods , Haplotypes , Myiasis/etiology , Sequence Analysis, DNA/methods
4.
Acta Trop ; 138 Suppl: S62-8, 2014 Oct.
Article in English | MEDLINE | ID: mdl-24927686

ABSTRACT

The Old World screwworm (OWS) fly, Chrysomya bezziana, is an obligate parasite of livestock, and the myiasis caused by its larval infestations is economically important in Indonesia. The current spatial distribution of such a pest depends on two main factors: the current environmental conditions in which it can survive; and, its ability to occupy those environments by dispersal, which can be inferred from phylogeography and population genetics. These indicate that all OWS flies in Indonesia have mitochondrial cytochrome b (cyt b) haplotypes of the Asian lineage, and the regional separation of its four sub-lineages is the result of infrequent long-distance dispersal. We report the first investigation to associate regional cyt b sub-lineages of the OWS fly with environmental variables. Principal Components Analysis was used to demonstrate that these sub-lineages are associated with very similar macro-climates throughout Indonesia. Then, a species distribution model for the OWS fly in Indonesia was obtained by using the Maxent program. This indicated that elevation captured information not given by other environmental variables, and cattle density provided the most useful information by itself. The results of our study provide some important leads for future research, which will require better, stratified sampling.


Subject(s)
Diptera/growth & development , Phylogeography , Animals , Cattle , Cytochromes b/genetics , DNA, Mitochondrial/genetics , Genetics, Population , Genotype , Geography , Haplotypes , Indonesia
5.
Acta Trop ; 138 Suppl: S69-75, 2014 Oct.
Article in English | MEDLINE | ID: mdl-24754921

ABSTRACT

The myiasis fly Chrysomya bezziana Villeneuve (Diptera: Calliphoridae) is an obligate parasite of body orifices and unnatural openings or wounds of vertebrates. It is a major pest of livestock and responsible for economic losses throughout the Old World. Two chemical lures were tested in the present study to assess their effectiveness at trapping Ch. bezziana. Bezzilure B contains a synthetic lure of 2-mercaptoethanol originally identified from cattle wound volatiles. POC is a synthetic lure comprising 4-methyl phenol, 3-propyl phenol and racemic 1-octen-3-ol, originally identified from volatiles of ox odour and now used to control tsetse flies (Diptera: Glossina). Bezzilure B and POC lures were tested alone, and in combination, in a laboratory free flight room bioassay and in a field trial. Sticky traps were used to capture males and females of Ch. bezziana and to determine the efficacy of the lures. In the laboratory, Bezzilure B caught significantly more male and female flies than Bezzilure B+POC (p<0.001). Similarly, in the field, treatment significantly affected the total number of Ch. bezziana caught (p<0.001) but, contrastingly, Bezzilure B+POC caught significantly more flies than Bezzilure B (p<0.05). The differing results between the laboratory and field may simply reflect the different assays and could suggest different roles of semiochemicals at different operational distances. Although ineffective on its own, POC has a synergistic effect with Bezzilure B to increase fly catches in the field: by proportion, Bezzilure B+POC was 2.17 times as efficient as Bezzilure B for Ch. bezziana, and 1.16-2.68 times as efficient for other flies depending on the species collected.


Subject(s)
Diptera/physiology , Pheromones/pharmacology , Volatile Organic Compounds/pharmacology , Animals , Diptera/drug effects , Diptera/growth & development , Drug Synergism , Female , Male , Pheromones/chemistry , Pheromones/isolation & purification , Volatile Organic Compounds/chemistry , Volatile Organic Compounds/isolation & purification
6.
Acta Trop ; 138 Suppl: S49-55, 2014 Oct.
Article in English | MEDLINE | ID: mdl-24727206

ABSTRACT

The Old World screwworm (OWS) fly, Chrysomya bezziana (Diptera: Calliphoridae), is a major economic and welfare problem for humans and animals in the Old World tropics. Using a bootstrapped log likelihood ratio test of the output of Procrustes principal components and canonical variates analyses for a small sample of museum specimens from which 19 2D wing landmarks had been collected: (1) a consistent and statistically significant difference exists between landmark configurations derived from wings of pinned specimens and those removed from the body and mounted on slides; (2) a highly statistically significant sexual dimorphism in wing morphometry was identified; and (3) a highly statistically significant difference in wing morphometry between populations of the OWS fly from Africa (Tanzania, South Africa Sudan, Zaire, Zimbabwe,) and Asia (Sumba, Indonesia) exists. These results show that wing orientation and gender must be considered when conducting morphometric investigations of OWS fly wings. The latter result is also consistent with results from previous molecular and morphological studies, which indicate there are two distinct genetic lineages within this species. Wing morphometry holds great promise as a practical tool to aid in identification of the geographical origin of introductions of this important pest species, by providing diagnostic markers to distinguish geographical populations and complement molecular diagnostics.


Subject(s)
Biometry/methods , Diptera/anatomy & histology , Diptera/classification , Entomology/methods , Wings, Animal/anatomy & histology , Africa , Animals , Indonesia , Museums
7.
Parasitol Res ; 113(5): 1629-40, 2014 May.
Article in English | MEDLINE | ID: mdl-24553979

ABSTRACT

There are only three fly species that are obligate agents of traumatic myiasis of humans and livestock: a single species of flesh fly, Wohlfahrtia magnifica (Sarcophagidae), and two species of blow flies, Chrysomya bezziana and Cochliomyia hominivorax (Calliphoridae). The morphology of their first instar larvae is thoroughly and consistently documented here with light microscopy photographs and scanning electron microscopy micrographs. The following morphological structures are documented: pseudocephalon, antennal complex, maxillary palpus, oral ridges, thoracic and abdominal spinulation, spiracular field, posterior spiracles and cephaloskeleton. New diagnostic features drawn from the cephaloskeleton and the spinulation of abdominal segments, including the anal pad, are discovered and extensively described. Earlier descriptions in the literature are revisited, and major discrepancies between these and the results of the current study are discussed. The present results allow clarification, correction and, especially, complementation of information provided by earlier authors. The relatively distant taxonomic position of all three species is evidence that obligatory myiasis has arisen independently, and the extensively similar morphology in the first instar larvae of Chrysomya bezziana, Cochliomyia hominivorax and W. magnifica in comparison to necrophagous species, especially the enhancement of the anterior part of the cephaloskeleton and the segmental spinulation, is therefore best interpreted as homoplasic adaptations to a life strategy as obligate vertebrate parasites. An identification key for first instar larvae of all obligatory traumatic myiasis agents of mammals is provided.


Subject(s)
Diptera/anatomy & histology , Sarcophagidae/anatomy & histology , Animals , Diptera/ultrastructure , Larva/anatomy & histology , Microscopy , Microscopy, Electron, Scanning , Myiasis/parasitology , Sarcophagidae/ultrastructure
8.
Int J Parasitol ; 42(8): 729-38, 2012 Jul.
Article in English | MEDLINE | ID: mdl-22664061

ABSTRACT

Phylogenetic, genealogical and population relationships of Chrysomya bezziana, the Old World screwworm fly (OWSF), were inferred from DNA sequences of mitochondrial cytochrome b (cyt b), nuclear elongation factor-1α (EF-1α) and nuclear white eye colour (white), using sequences of Chrysomya megacephala and Chrysomya rufifacies as outgroups. Cyt b (717bp, 754 specimens), EF-1α (361bp, 256 specimens) and white (577bp, 242 specimens) were analysed from up to two African and nine Asian countries, including 10 Indonesian islands. We show that OWSF occurs as distinctive African and Asian lineages based on cyt b and white, and that there is a marked differentiation between Sumatran and Javan populations in Indonesia, supported by the genealogy and analysis of molecular variance of cyt b alone. Four cyt b sub-lineages are recognised in Asia: only 2.1 occurs on the Asian mainland, from Yemen to Peninsular Malaysia; only 2.2, 2.3 and 2.4 occur in central Indonesia; 2.4 predominates on New Guinea; and 2.1 co-occurs with others only on Sumatra in western Indonesia. This phylogeography and the genetic distances between cyt b haplotypes indicate pre-historic, natural dispersal of OWSF eastwards into Indonesia and other Malesian islands, followed by vicariant evolution in New Guinea and central Indonesia. OWSF is absent from Australia, where there is surveillance for importation or natural invasion. Judged by cyt b haplotype markers, there is currently little spread of OWSF across sea barriers, despite frequent shipments of Australian livestock through Indonesian seas to the Middle East Gulf region. These findings will inform plans for integrated pest management, which could be applied progressively, for example starting in East Nusa Tenggara (central Indonesia) where OWSF has regional cyt b markers, and progressing westwards to Java where any invasion from Sumatra is unlikely. Cyt b markers would help identify the source of any re-emergence in treated areas.


Subject(s)
Diptera/classification , Phylogeny , Animals , Asia , Cytochromes b/genetics , Diptera/genetics , Diptera/physiology , Insect Proteins/genetics , Molecular Sequence Data , Peptide Elongation Factor 1/genetics , Pest Control , Phylogeography
9.
Med Vet Entomol ; 23 Suppl 1: 43-50, 2009 Jun.
Article in English | MEDLINE | ID: mdl-19335829

ABSTRACT

A previous study had identified an African and an Asian race of the Old World screwworm fly, Chrysomya bezziana Villeneuve (Diptera: Calliphoridae), based on the 3' terminal 279 basepairs (bp) of the mitochondrial cytochrome b gene. The current study improved the phylogeographic resolution of cytochrome b for this species by characterizing more of the gene (the 3' terminal 715 bp) and by sampling more geographical populations, including Oman, Iran, Hong Kong and the Indonesian islands of Sulawesi and East Sumba. Strong support was found for recognizing an African race, but not for a monophyletic Asian race. The cladistic and genealogical relationships among the Asian populations were complex. There was sufficient genetic homogeneity throughout separate regions (mainland Asia and each Indonesian island) to suggest that there are no reproductive barriers within each region that might necessitate the production of more than one strain for control by the sterile insect technique (SIT). Primers were designed for the amplification by polymerase chain reaction of two nuclear loci, the highly conserved elongation factor-1alphagene and the less conserved white gene, and the preliminary results indicated that these genes showed the same pattern of small-scale regional variation as cytochrome b. The cytochrome b haplotypes are useful markers for identifying the geographical origins of any emerging infestations of the species: the absence of Indonesian and African haplotypes in the Middle East demonstrates that the large-scale transport of livestock is not spreading Old World screwworm.


Subject(s)
Cell Nucleus/genetics , Cytochromes b/genetics , Diptera/genetics , Mitochondria/genetics , Animals , Base Pairing , DNA/genetics , DNA/isolation & purification , DNA Primers , Diptera/classification , Gene Amplification , Geography , Phylogeny
10.
Med Vet Entomol ; 23 Suppl 1: 51-8, 2009 Jun.
Article in English | MEDLINE | ID: mdl-19335830

ABSTRACT

Fly larvae were collected from 181 cases of traumatic myiasis in livestock in 10 regions of four countries in the Middle East Gulf region: Iran, Iraq, Saudi Arabia and Oman. The predominant fly species responsible for cases was the Old World screwworm (OWS) fly, Chrysomya bezziana Villeneuve (Diptera: Calliphoridae). In cases from Iran and Oman, which included non-OWS fly species, OWS fly was found solely responsible for 67.6% of cases and jointly with other fly species for a further 12.7% of cases. The major hosts were sheep and goats, together comprising 84.6% of the total, which reflects their predominance among the livestock of these Gulf countries. The major site of wounding on sheep and goats was the tail (40.3%), followed by female genitalia (14.0%). The 3' terminal 715 nucleotides of the mitochondrial cytochrome b gene were sequenced for 178 larvae of OWS. Five haplotypes were identified: three had been recorded previously in the region (two were common throughout and one was unique to Oman), and two were newly identified, one from southern Iraq and the other from Saudi Arabia, both in regions sampled for the first time. The haplotypes varied from one another only at one or two nucleotide sites, equivalent to an intraspecific difference of 0.14-0.28% across the entire 715-bp fragment. There was a single statistically significant association between host species and haplotype in Saudi Arabia, a first such record for OWS fly. The small degree of genetic diversity between geographical populations of OWS fly within the Gulf region suggests that a single Gulf colony could be used to implement the sterile insect technique within an integrated control programme.


Subject(s)
Diptera/genetics , Genetic Variation , Myiasis/veterinary , Screw Worm Infection/veterinary , Sterilization/methods , Animals , Animals, Domestic/parasitology , Female , Iran/epidemiology , Iraq/epidemiology , Male , Myiasis/epidemiology , Myiasis/genetics , Oman/epidemiology , Saudi Arabia/epidemiology , Screw Worm Infection/epidemiology , Screw Worm Infection/genetics
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