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Biomedical subjects

T M Craig

Publications and source records attributed to T M Craig.

At least 37 records · Page 2Linked to original sources
PubMed1993

Lynxacarus radovskyi infestation in a cat.

An adult domestic short-hair cat from south Texas was examined because of excessive dandruff on the back, neck, thorax, and hind limbs. Removal of a few hairs for microscopic evaluation revealed Lynxacarus radovskyi, the cat fur mite. The small (< 0.5 mm) mite could be readily identified by its laterally compressed body and its characteristic grasping of the hair shaft between the gnathosoma and palpi. Thus far, this mite has been identified as a parasite of cats in warm, humid environments. The number of parasites and apparent discomfort in cats varies considerably, from massive infestation with little discomfort to few mites and marked pruritus. Acaricides that are effective against other ectoparasites of cats apparently are effective in controlling L. radovskyi.

Animals↗
PubMed1993

Diffuse cutaneous leishmaniasis in a cat.

An adult long-haired domestic cat native to South Texas developed signs consistent with diffuse cutaneous leishmaniasis. Cutaneous leishmaniasis, caused by Leishmania mexicana, was initially diagnosed from lesions confined to the left ear. A radical pinnectomy was done and the cat was returned to its owner. Two years later, lesions developed at the stump, and lesions later developed on the cat's muzzle and nasal mucosa. All of the lesions contained numerous L mexicana amastigotes. Several treatment regimens were attempted, but without evidence of resolution. The cat was tested multiple times for evidence of impaired immunologic competence and was found to be normal. The cat failed to respond to Leishmania antigen given interdermally (Montenegro test) on several occasions. On one occasion, however, there was partial regression of the lesions following the Montenegro test. Cats in areas endemic for cutaneous leishmaniasis (South Texas) may serve as sentinels for the agent. The epidemiology of the infection in this area is largely unknown, as is the importance of cats in the spread of disease.

Animals↗
PubMed1993

Ultrastructure of Hepatozoon canis in the dog.

The ultrastructure of several stages of Hepatozoon canis found in dogs with clinically diagnosed infections was determined using transmission electron microscopy. Stages were found in skeletal muscle tissue that corresponded to the 'onion skin' cyst stage, as described at the light microscopic level, and were composed of an electron-transparent material that appeared to radiate from a central core. Larger cysts, walled off by fibroblasts, contained a transformed host cell located centrally within them. The parasitic stage within these transformed cells contained numerous organelles including mitochondria and Golgi apparatus, and was singularly nucleated. In cardiac muscle, a meront was observed which produced merozoites by ectomerogony. Adjacent to this meront was a granuloma containing merozoites within mononuclear phagocytes which may either serve as a reservoir of parasites for reinfection of the host or differentiate into the circulating gamont stage of the parasite. Gamonts were found within parasitophorous vacuoles inside circulating neutrophils. They had a condensed cytoplasmic appearance and were extremely electron dense with respect to other observed parasite stages. In vitro cultivation of parasitized neutrophils resulted in the appearance of a stage of the parasite with altered ultrastructure compared with gamonts found in circulating neutrophils. This stage was judged to be a possible gamete stage of the parasite.

Animals↗
PubMed1993

Anthelmintic resistance.

In populations of livestock in which anthelmintics have become the only means of control, individual worms in some species of helminths evade the effects of specific anthelmintics. If these resistant individuals are selected (by removing the susceptible individuals in the population) then the resistant worm population on individual farms becomes dominant in both numbers and effect. This selection of anthelmintic resistant populations is most often reported in equids and small ruminants (the hosts in which anthelmintics are used most frequently). There is little evidence of anthelmintic resistance by Ostertagia in cattle but an understanding of the problem in other grazing species may aid in delaying its onset. Benzimidazole/phenothiazine resistance by small strongyles in horses in widespread. Resistance by various geographic strains of Haemonchus, Teladorsagia and Trichostrongylus against all of the commonly used classes of anthelmintics in small ruminants has been verified. The failure of levamisole to remove adult Ostertagia ostertagi from cattle has been reported in several geographical areas. Resistance is an individual farm problem and each premise has to be evaluated as to which anthelmintics can be used. Drug rotation, especially rapid rotation (less than 1 year) selects for multiple drug resistance. Epidemiologic treatment selects for resistance, but if properly used, requires considerably fewer treatments to prevent disease and the development of resistant populations will be slowed. A combination of strategic and tactical treatments along with evaluation of anthelmintics will be required to enable producers to raise livestock in maximum production units.

Animals↗
PubMed1993

Spiculopteragia spiculoptera and S. asymmetrica (Nematoda: Trichostrongyloidea) from red deer (Cervus elaphus) in Texas.

Specimens of Spiculopteragia spiculoptera and S. asymmetrica were recovered from the abomasa of five of ten naturally infected red deer (Cervus elaphus) in Texas (USA). Female specimens of Spiculopteragia were present in all five animals. Male specimens of S. spiculoptera and S. asymmetrica were present in one of five and three of five red deer, respectively. Spiculopteragia spiculoptera has not previously been recognized in the United States and the present report constitutes the first records of Spiculopteragia spp. in red deer from North America. It is likely that species of Spiculopteragia have been introduced to North America with the import of exotic cervids on several occasions. Focal populations of these nematodes have been established in North America; however, distribution of the parasites likely coincides with areas of residence of introduced populations of red deer and fallow deer (Cervus dama) in the Nearctic.

Abomasum↗
PubMed1993

Longistrongylus curvispiculum (Nematoda: Trichostrongyloidea) in free-ranging exotic antelope in Texas.

Longistrongylus curvispiculum was recovered from free ranging sable (Hippotragus niger), addax (Addax nasomaculatus) and biesa oryx (Oryx beisa) on two ranches in central Texas (USA). These nematodes represented a small portion of the total abomasal worm burden dominated by Haemonchus contortus. Female L. curvispiculum easily could be confused with other ostertaginae, but the spicules of the males were diagnostic.

Abomasum↗
PubMed1992

Eosinophilic gastroenteritis with encapsulated nematodes in a horse.

A 3-year-old Quarter Horse gelding admitted for evaluation of weight loss, signs of depression, and dermatitis of the coronary bands was found to have eosinophilic gastroenteritis. Intralesional nematodes identified as Strongylus edentatus were seen in multiple microscopic sections of the small colon, suggesting a parasitic cause of the disease.

Animals↗
PubMed1992

Efficacy of moxidectin against an ivermectin-resistant strain of Haemonchus contortus in sheep.

The efficacy of moxidectin was determined against ivermectin-susceptible and resistant strains of Haemonchus contortus. At the onset of the trial, 40 lambs were each infected with 5000 third stage larvae of one of two strains of Haemonchus contortus. The lambs were randomly sorted into eight treatment groups 28 days post-infection and were treated as follows: Group 1, susceptible strain with no treatment; Group 2, resistant strain with no treatment; Group 3, susceptible strain treated with 0.2 mg moxidectin kg-1 body weight; Group 4, resistant strain treated with 0.2 mg moxidectin kg-1; Group 5, resistant strain treated with 0.4 mg moxidectin kg-1; Group 6, susceptible strain treated with 0.2 mg ivermectin kg-1; Group 7, resistant strain treated with 0.4 mg ivermectin kg-1; Group 8, resistant strain treated with 0.8 mg ivermectin kg-1. The lambs were killed 1 week post-treatment. Comparisons were made among groups based on the number of eggs per gram of feces on the day of treatment and the numbers of worms recovered from each lamb. Both moxidectin and ivermectin were effective in removing susceptible Haemonchus with efficacies of 100% and 99.7%, respectively. The efficacy of moxidectin against the resistant strain was 99.9% and 100% at 0.2 mg kg-1 and 0.4 mg kg-1, respectively, whereas there were only 38.8% and 53.1% efficacies in the lambs treated with 0.4 mg ivermectin kg-1 and 0.8 mg kg-1 body weight, respectively.

Animals↗
PubMed1992

Resistance to ivermectin by Haemonchus contortus in goats and calves.

Efficacy of ivermectin on susceptible or resistant populations of the parasitic nematode Haemonchus contortus was determined in cattle and goats held in a barn. Goats were each infected with 3000 infective, ivermectin-susceptible or -resistant H. contortus larvae on day 0 and reinfected with 2000 infective larvae on day 24. Goats were treated orally with 600 micrograms kg-1 ivermectin on day 31. No significant differences were detected in blood packed cell volume (PCV) or total protein (TP), prepatent period, or epg among the four groups of goats that were each infected with one of four parasite strains (one susceptible, three resistant). There were no differences among the four parasite strains in the numbers of infective larvae that developed to the third larval stage from fecal cultures or in the viability of cultured infective larvae when held in the laboratory at 27 +/- 1 degrees C for 14 weeks. After treatment with ivermectin, there were significant differences among the parasite strains in PCV, TP, and epg. Total worm counts were reduced by 94 to 97% with three times the recommended dose. Immature and adult Skrjabinema ovis were also present in two treated goats. In a second test, one goat infected once with 10,000 infective larvae of a resistant strain of H. contortus and then treated with nine doses of ivermectin, increasing from 500 to 2000 micrograms kg-1 over a period of 133 days, had 35 adult worms at necropsy. In a third test, three calves were readily infected with an ivermectin-resistant strain of H. contortus from goats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effects of low levels of lice and internal nematodes on weight gain and blood parameters in calves in central Texas.

The effects of low levels of both biting and sucking lice, a mixed population of nematodes, and a combination of all these parasites were evaluated in calves held in a barn with no environmental controls in central Texas. Observations at 122 sites on each animal for 16 wk consecutively in 1987 revealed that the largest numbers of all louse species [Haematopinus eurysternus (Nitzsch). Linognathus vituli (L.), and Bovicola bovis (L.)] occurred 3-7 wk after infestation. In 1988 L. vituli populations decreased rapidly after the 3rd wk and B. bovis remained fairly constant for 20 wk consecutively. Average nematode egg counts increased to approximately 300 eggs per gram of feces in 1987 and approximately 600 eggs per gram of feces in 1988. The nematodes Ostertagia ostertagia, Haemonchus placei, Oesophagostomum radiatum, Cooperia spp., and Trichostrongylus spp. were present at the end of the study in both years as determined by necropsy. No significant differences in erythrocyte count, mean cell volume, hematocrit, hemoglobin concentration, leukocyte counts, or serum albumin concentration were detected. However, significant increases in total serum protein concentration and serum globulin levels in calves harboring both groups of parasites were observed. Mean weight gain in calves infested with lice and nematodes was 11.4 and 10 kg less than that of uninfested controls during 16 wk in 1987 and 20 wk in 1988, respectively.

Animals↗
PubMed1992

Efficacy of two formulations of albendazole against liver flukes in cattle.

Albendazole (10 mg/kg of body weight) was administered as a drench suspension or as a feed additive to 24 cattle with naturally acquired infections of Fasciola hepatica and Fascioloides magna. Cattle were euthanatized 16 to 30 days after treatment, and the number of viable flukes was counted. Viable F hepatica and F magna were decreased by 91.4% and 70.6% for drench administration and by 82.9% and 71.9% for the feed additive treatment, respectively. There was no significant difference between the efficacy of the 2 formulations in decreasing viable fluke numbers, compared with untreated controls.

Administration, Oral↗
PubMed1991

Nutritional and dietary interrelationships with diseases of grazing beef cattle.

This article describes current methods of controlling acute bovine pulmonary emphysema (ABPEE) and edema, lungworm and gastrointestinal nematodes, and bloat in grazing beef cattle. Success in handling outbreaks of these conditions and in their prevention depends on an understanding of their epidemiology and pathogenesis. Supplementation with ionophore antibiotics is effective in prevention of ABPEE and bloat and may also prevent other diseases of cattle that graze lush pastures.

Acute Disease↗
PubMed1991

Effect of milbemycin oxime against Ancylostoma caninum in dogs with naturally acquired infection.

Twenty-six mixed-breed (14 males, 12 females) dogs were used in a double-blind study to evaluate the effect of milbemycin oxime against naturally acquired infection with Ancylostoma caninum. Dogs were ranked and paired, on the basis of number of hookworm eggs/g of feces, and treatment was randomly assigned. Each dog was given either the study drug or placebo (1 tablet/11.4 kg [0.5 mg/kg] of body weight). Eggs per gram of feces enumeration was done on days 3 and 7 after treatment, and dogs were euthanatized on day 7. On day 3, 5 of the 13 dogs in the milbemycin-treated group had hookworm eggs in the feces (results of the McMaster test). In these dogs, mean number of eggs per gram of feces had decreased markedly (from 5,289 to 452) and, by day 7, was 114. At necropsy, 16 A caninum adults were recovered from 2 of the milbemycin-treated dogs. On day 3, 12 of the 13 dogs in the placebo-treated group had hookworm eggs in the feces. Mean number of eggs per gram of feces in these dogs decreased slightly (from 5,243 to 2,646), but did not decrease further by day 7. A mean number of 54.4 A caninum adults was recovered from 12 of the 13 placebo-treated dogs at necropsy. Milbemycin oxime had 97.8% efficacy against A caninum. Results also indicated that milbemycin oxime may be effective against Trichuris vulpis, but not against Dipylidium caninum.

Ancylostomiasis↗
PubMed1991

Efficacy of nitroscanate against naturally acquired infection with Ancylostoma caninum, Dipylidium caninum, and Trichuris vulpis in dogs.

Eighteen dogs with naturally acquired helminth infections were used to evaluate the efficacy of nitroscanate against Ancylostoma caninum, Dipylidium caninum, and Trichuris vulpis. Approximately 15 minutes before treatment, the dogs were given 100 to 200 g of canned dog food. Ten dogs were treated with nitroscanate (50 mg/kg of body weight, PO), and 8 dogs were given placebo tablets PO. The dogs were euthanatized and necropsied 10 days after treatment and helminths were recovered from the small intestine and cecum. On the basis of the number of worms recovered from treated dogs vs the number recovered from control dogs, we determined the efficacy of nitroscanate to be 99.6% against A caninum, 99.8% against D caninum, and 0% against T vulpis.

Ancylostoma↗
PubMed1990

Effects of horn fly and house fly (Diptera: Muscidae) larvae on the development of parasitic nematodes in bovine dung.

Laboratory studies were conducted to determine the effects of horn fly, Haematobia irritans (L.), and house fly, Musca domestica L., larvae on the development of a mixed population of parasitic nematodes in compressed and crumbled bovine dung. Fresh dung (100 g per sample) from a single calf passing trichostrongyle type eggs was infested with 150 horn fly or 150 house fly eggs. After 14-15 d, more horn flies and house flies had emerged from the compressed dung than from the crumbled dung, but more third stage parasitic nematode larvae were recovered from the crumbled dung containing either fly species than from dung containing no flies.

Animals↗
PubMed1990

Naturally occurring apicomplexan acute interstitial pneumonitis in thick-billed parrots (Rhynchopsitta pachyrhyncha).

This report describes acute interstitial pneumonitis due to an apicomplexan parasite with schizogony in endothelial cells of pulmonary vessels accompanied by early and metrocyte stages of sarcocysts in the heart of a thick-billed parrot (Rhynchopsitta pachyrhyncha). The pattern of this disease is similar to that of the acute phase (approximately 10-15 days postinoculation) of experimental infections of budgerigars, Melopsittacus undulatus, with high doses of sporocysts of Sarcocystis falcatula.

Acute Disease↗
PubMed1989

Efficacy of triclabendazole against fascioloidiasis (Fascioloides magna) in naturally infected white-tailed deer (Odocoileus virginianus).

The efficacy of triclabendazole was evaluated in the treatment of naturally acquired Fascioloides magna infections in white-tailed deer (Odocoileus virginianus). Twenty white-tailed deer were captured on the Welder Wildlife Refuge (Sinton, San Patricio County, Texas, USA) and maintained in a 64 x 64 m deer enclosure. Ten deer were given a 5% suspension of triclabendazole orally at a dosage of 10 mg/kg body weight and 10 deer were given a placebo. Three wk later the deer were euthanized and examined for parasites. At necropsy 19 deer were infected. All specimens of F. magna from the tissues of the triclabendazole treated deer were dead or severely affected by the drug as indicated by changes in their size, color, movement and texture relative to those from control deer. The drug was considered 100% effective against this parasite. Adverse reactions of the deer to the drug were not observed.

Animals↗