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Biomedical subjects

Douglas D Colwell

Publications and source records attributed to Douglas D Colwell.

12 recordsLinked to original sources
PubMed2005

Species composition of Gasterophilus spp. (Diptera, Oestridae) causing equine gastric myiasis in southern Italy: parasite biodiversity and risks for extinction.

Horse gastrointestinal myiasis caused by larvae of Gasterophilus spp. (Diptera, Oestridae) flies has a worldwide distribution and, where present, it is primarily caused by larvae of Gasterophilus intestinalis and Gasterophilus nasalis. Other species, i.e., Gasterophilus inermis, Gasterophilus pecorum and Gasterophilus haemorrhoidalis, present in different or in the same regions of the gastrointestinal tract, were only occasionally reported in very limited areas of eastern European Countries and in central Italy. With the aim to contribute data on the species composition of Gasterophilus and on the seasonal variation of the infection pattern in southern Italy, 152 native horses were necropsied from January to December 2003 and Gasterophilus larvae were collected from the stomach, the small intestine and the rectum of each of them. On the whole, 125 (82.2%) horses were infected by larvae of Gasterophilus spp. and 214 second stage larvae (L2) and 13,342 third stage larvae (L3) collected. Five species of Gasterophilus were identified with the following prevalence: G. intestinalis=95.2%, G. nasalis=44.8%, G. inermis=15.2%, G. pecorum=2.6% and G. haemorrhoidalis=0.8%. L3 were retrieved throughout the observation period with the highest mean burdens from January to August 2003 while the lowest mean was registered from September to November 2003. L2 were collected in February-March 2003 and from September to December 2003. The majority of the animals (n=66, 43.4%) were infected with a single Gasterophilus species, however, 45 animals (29.6%) harboured 2 species, 12 animals (7.9%) 3 species and 2 animals (1.3%) 4 species. The trend of abundance in the L3 of G. intestinalis and G. nasalis, the most represented species, was highly concordant (r=0.5, p<0.001). A retrospective comparison of our results and of other data from four seasons of observation (1983-1986) in central Italy showed that the number of G. inermis, G. pecorum and G. haemorrhoidalis have been decreasing relative to G. intestinalis and G. nasalis which may suggest tendency toward the extinction of the three former species of Gasterophilus.

Age Factors↗
PubMed2004

Report in Europe of nasal myiasis by Rhinoestrus spp. in horses and donkeys: seasonal patterns and taxonomical considerations.

Two species of Rhinoestrus (i.e. Rhinoestrus purpureus (Brauer) and Rhinoestrus usbekistanicus Gan) cause nasal myiasis in horses, donkeys and zebras. In the past 15 years myiasis caused by R. purpureus has been reported in Egypt and by R. usbekistanicus in Senegal and Niger, both in horses and in donkeys. With the aim to investigate the presence of this myiasis in autochthonous horses and donkeys from southern Italy and to study the seasonal trend of larval infection, 212 native horses were necropsied in two slaughterhouses in the Apulia region (site A) from January to November 2003, and 120 native horses and two donkeys in one slaughterhouse in Sicily (site B) from January to October 2003. Thirteen of 212 and 5 of 120 horses examined from sites A and B, respectively, were infected by nasal bot fly larvae. Both donkeys examined were positive. Two hundred and thirteen larvae, representing all stages, were collected from the throat region, the turbinates and beyond the lamina cribrosa of the ethmoid bone, in the cerebral cavity. Third larval stages were retrieved from April to September with the highest mean burden in site A in May and in July in site B. The simultaneous presence all three larval stages at site B suggests the existence of two or more overlapping generations. Larvae were identified on the basis of peritreme structures and arrangement of the spines on the dorsal surface of the third segment. Some L3 collected from sites A and B presented morphological characteristics of both R. usbekistanicus and R. purpureus. The presence of mixed features on the L3 of Rhinoestrus collected from the same animals may be explained by the existence of a single species of Rhinoestrus presenting different morphotypes or of two species of Rhinoestrus which are both present in southern Italy since this area is midway between eastern and African countries where these two species have been reported.

Age Factors↗
PubMed2004

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.

Animals↗
PubMed2003

Effect of treatment on the dynamics of circulating hypodermin C in cattle naturally infested with Hypoderma lineatum (Diptera: Oestridae).

An antigen capture ELISA, using a murine monoclonal antibody recognising recombinant hypodermin C (rHyC), was used to evaluate the influence of early treatment with eprinomectin (Eprinex) or fenthion (Spotton) on the kinetics of circulating hypodermin C in calves naturally infested with Hypoderma lineatum. No viable larvae were collected from treated animals, whereas a variable number of warbles were found in control animals. Treatment provoked a decrease in circulating HyC levels that was significant 9 days post-treatment (p.t.). Circulating antigen levels in the treated cattle remained detectable for approximately 99 days p.t. In contrast, control animals had no detectable antigen at 64 days p.t., 42 days earlier than in the treated animals. These results suggest that larvae were either gradually killed, resulting in slow release of antigen or they were encapsulated, leading to the slow liberation of antigen. Kinetics of circulating HyC did not differ among the two insecticide treatments. Antibodies persisted, in all groups, throughout the 120-day study. These results suggest that the antigen capture ELISA will be useful as a technique for detecting successful treatment of cattle grub infestations and for the detection of new infestations in previously infested cattle.

Administration, Topical↗
PubMed2002

Linognathus vituli (Anoplura: Linognathidae): population growth, dispersal and development of humoral immune responses in nai;ve calves following induced infestations.

Growth of Linognathus vituli populations following establishment at a point source was followed for 16 weeks on eight louse-naïve Holstein calves. Dispersal of lice from the point of infestation (withers) was monitored by examination of known louse predilection sights. Mean louse indices increased during the initial weeks reaching maximum mean values at 8 weeks post-infestation (p.i.). Subsequently, mean indices decreased, reaching a plateau that persisted through weeks 14 and 15 p.i. There was little movement away from the withers until 5 weeks p.i. Subsequently, numbers of lice on the withers declined, while increasing at sites on the head. A few lice were noted on the dewlap and topline sites. Host antibody responses to crude nymph antigens, measured by enzyme-linked immunosorbent assay (ELISA), were generally evident within 2-4 weeks of infestation. Examination of individual host data showed louse populations could be categorized relative to the mean population size for the group. Two animals were considered 'chronic', having louse populations that persisted throughout the study and whose louse indices were >150% of the group mean. Two animals were classified as 'resistant' having lice present for only a portion of the study and whose louse indices <40% of the group mean. The remaining animals had louse indices between 62 and 137% of the group mean. Antibody profiles of the individuals were not as clearly categorized, although the 'resistant' animals were only positive for short periods of time, roughly corresponding to the time when lice were observed.

Animals↗
PubMed2002

Detection of circulating hypodermin C: an antigen capture ELISA for diagnosis of cattle grub (Diptera: Oestridae) infestations.

An antigen capture assay for the detection of circulating hypodermin C was developed for diagnosis of hypodermosis. A murine monoclonal antibody to recombinant hypodermin C was raised using rapid immunization and a one-step hybridization-cloning technique. A highly reactive, specific monoclonal antibody was tested using sera spiked with known quantities of purified, native hypodermin C or with recombinant hypodermin C. Sensitivity of 96.4% and specificity of 95.6% for the antigen capture assay was assessed using a panel of sera from animals unexposed to cattle grubs and from cattle with palpation proven cattle grub infestations. Data from this panel of sera was used to establish the cut-off OD for further testing. The kinetics of circulating hypodermin C was assessed using the assay in three groups of cattle artificially infested with 50, 100 or 200 first instar Hypoderma lineatum. Antigen was first detected approximately 6 weeks after infestation. The amount of antigen detected increased in each group of animals reaching peaks at different times in each group. Levels of antigen fell quickly following arrival of grubs at the back and completion of the molt to second instar.

Animals↗
PubMed2002

Persistent activity of topical ivermectin against artificial infestations with Hypoderma lineatum (Diptera: Oestridae).

In controlled experiments utilizing artificial infestations, a topical formulation of ivermectin (IVOMEC Pour-On for Cattle) was 100% effective against migrating first instar Hypoderma lineatum for 3 weeks following treatment. Larvae were apparently killed early in the infestation as no significant level of specific antibodies was found in the treated calves. At 4 weeks post-treatment the efficacy remained high at 96%; mortality of larvae in the one calf in which warbles were observed and from which mature third instars were collected, was higher than that seen in the untreated calves, indicating some level of treatment induced effect. No specific antibodies were detected in calves that did not develop palpable warbles. Antibody kinetics in those calves from which viable larvae emerged were typical. The length of activity of this product against early stages of the cattle grub makes it practical to apply treatment up to 3 weeks before the end of fly activity.

Administration, Topical↗
PubMed2002

Persistent activity of moxidectin pour-on and injectable against sucking and biting louse infestations of cattle.

To evaluate the persistent activity of pour-on and injectable moxidectin against natural challenge by sucking (predominantly Linognathus vituli) and chewing (Bovicola bovis) cattle lice, 96 mixed-breed calves that had been treated to remove all lice were blocked by body weight and randomly allocated to three treatments: untreated control, moxidectin at 500 microg/kg by topical application and moxidectin at 200 microg/kg by subcutaneous injection. Twelve pens were blocked into groups of four and randomly allocated to four challenge times: 14, 21, 28 and 35 days post-treatment. Treatment groups were assigned to challenge pens randomly. Two donor calves, with demonstrated infestations of both sucking and chewing lice, were introduced into each pen containing eight principal calves at the start of each challenge time. Donors remained in the challenge pen for 7 days. Principal calves were examined for lice, 7, 14, 21 and 28 days after donor removal using a standardized hair-parting technique. Moxidectin injectable prevented re-infestation with L. vituli for up to 42 days, but did not provide persistent activity against B. bovis longer than 35 days post-treatment. Moxidectin pour-on demonstrated persistent activity against both B. bovis and L. vituli for 42 days.

Administration, Topical↗
PubMed1998

Sex differences in opioid and N-methyl-D-aspartate mediated non-opioid biting fly exposure induced analgesia in deer mice.

There is evidence for sex differences in responses to noxious stimuli and in the expression and mediation of analgesia. In particular, results of investigations with swim stress and the more ethologically appropriate stress of predator odor exposure have suggested sex differences in N-methyl-D-aspartate (NMDA) receptor system involvement in the mediation of analgesia. Whether or not this sex difference generalizes to other environmental stressors is, however, not clear. Biting flies are a natural aversive stimuli commonly encountered by wild and domestic animals and humans. The present study examined the opioid and non-opioid mediated nociceptive (50 degrees C hot plate) responses of reproductive male and female deer mice, Peromyscus maniculatus, exposed to biting fly attack. A 30 min exposure to biting flies (stable flies, Stomoxys calcitrans (L.)) elicited a naloxone sensitive, opioid-mediated analgesia that was of a greater magnitude in males than in female deer mice. In contrast, a 5 min exposure to biting flies elicited a 'on-opioid' analgesia that was of similar magnitude in both sexes and insensitive to both naloxone and the specific kappa opiate antagonist, nor-binaltorphimine. In male mice this non-opioid analgesia was antagonised by the competitive NMDA antagonist, NPC 1262, while in reproductive females the biting fly-induced analgesia was insensitive to NPC 12626. These results show that there are sex differences in NMDA involvement in the mediation of the non-opioid analgesia arising from brief exposure to the stress of biting fly attack. These data from a common, natural environmental challenge support the presence of basic sex difference in NMDA involvement in the mediation of stress-induced analgesia.

Amino Acids↗