Strongylus vulgaris in the tunica media of arteries of ponies and treatment with ivermectin.

A preliminary investigation was made into the effect of fourth-stage Strongylus vulgaris larvae sequestered in the tunica media of ileocolic arteries of pony foals treated with ivermectin. The foals had been reared parasite-free, inoculated with infective larvae and given orally a placebo or ivermectin paste. Two foals received subsequently one or two further inoculations with larvae and treatment with ivermectin. Arteriography was used to identify the lesions in the ileocolic artery following inoculation and their regression following treatment. At necropsy, foals were examined for lesions and larvae grossly and histologically. Ivermectin was highly effective against fourth-stage larvae and those present in the media appeared not to unduly affect the integrity of the ileocolic artery. Increased numbers of larvae were not found in the media of foals receiving repeat inoculations and repeat treatments. Larvae were not found in the media of foals treated with a placebo. The major pathological changes in the arterial wall of all foals were attributed to infection with S. vulgaris and there was no strong tendency for the damaged arteries to return to normal after the S. vulgaris were removed.

Treatment of Goats Infected with the Lungworm Muellerius capillaris.

Goats naturally infected with Muellerius capillaris were treated with ivermectin subcutaneously once or twice at the rate of 200 or 300 mug/kg body wt or with fenbendazole per os twice at 15 mug/kg body wt. Goats ceased passing larvae 11 to 20 days after treatment, and except for one doe, larvae reappeared in feces 34 to 59 days after treatment. In sections of lung of ivermectin-treated goats, adult Muellerius had swollen body walls and disrupted intestinal tracts. Granulomas, some mineralized, were present. It is suggested that immature Muellerius were not destroyed by either anthelmintic and that following destruction of the adults, immature Muellerius resumed development to the adult stage and produced more first-stage larvae. Treatment of Muellerius may be more effective if repeated after approximately a 35-day interval.

Effectiveness of oxfendazole against early and later 4th-stage Strongylus vulgaris in ponies.

Twenty pony foals (reared worm free), 6.5 to 10 weeks of age, were inoculated with Strongylus vulgaris and allocated to 5 groups, each with 4 foals. One week after inoculation, 1 group of 4 foals was given oxfendazole (OFZ) at a dosage rate of 10 mg/kg of body weight, another group was given 2 such treatments 48 hours apart, and a 3rd group was given a placebo. All treatments were administered by stomach tube. Three weeks later, foals were euthanatized and necropsied in a test for efficacy against early 4th-stage larvae. Oxfendazole was 80% and 94.9% effective against early 4th-stage S vulgaris with 1 and 2 doses, respectively. A 4th group of 4 foals was given 2 treatments of OFZ, 48 hours apart, about 8 weeks after inoculation, and a 5th group was given a placebo. These foals were euthanatized and necropsied 5 weeks after treatment in a test for efficacy against later 4th-stage larvae. Two doses of OFZ were 96.6% effective against later 4th-stage larvae.

Experimental studies on the pathogenicity of Mycoplasma ovipneumoniae and Mycoplasma arginini for the respiratory tract of goats.

Mycoplasma ovipneumoniae and Mycoplasma arginini were the species of Mollicutes most commonly isolated from 175 goats with respiratory disease in Ontario. The pathogenicity of M. ovipneumoniae, strain B321B and M. arginini, strain D53e, was assessed in goats following endobronchial inoculation. One out of three two year old goats developed fever after inoculation with a pure culture of strain B321B, and it had extensive subacute fibrinous pleuritis when necropsied three weeks later. Neither of the remaining goats had lesions in the respiratory tract. Mycoplasma ovipneumoniae was recovered from one of the animals four days after inoculation, but not at necropsy from any of the goats, at which time a marked humoral immune response with growth inhibiting antibodies was detected. In a second experiment three four to five week old goats were inoculated with the same strain and three other goats were given placebo treatment. One experimental goat developed fever and coughing, and it had extensive subacute fibrinous pleuritis in the right side and pneumonia. Another goat had focal pneumonia in the left diaphragmatic lobe. Microscopically there was subacute hyperplastic suppurative bronchiolitis, atelectasis and nonsuppurative alveolitis. The infected animals did not clear the mycoplasma and not all of them produced antibodies. Mycoplasma arginini, strain D53e, did not induce lesions in any of four goat kids within 14 days after inoculation but did cause transient elevations in rectal temperature, circulating monocytes, circulating neutrophils and blood fibrinogen. Mycoplasma arginini was infective and immunogenic for all inoculated animals and showed a particular affinity for the tonsil. Thus, this study provides the first evidence that M. ovipneumoniae is pathogenic for goats causing pneumonia and pleuritis.(ABSTRACT TRUNCATED AT 250 WORDS)

Strongylus equinus: development and pathological effects in the equine host.

The development and pathological effects of Strongylus equinus were studied in 17 pony foals and one horse foal raised in isolation and examined at necropsy from seven days to 40 wk postinfection (PI). Following inoculation of 15000 +/- 6% or 16000 +/- 6% infective larvae by stomach tube foals were monitored for clinical signs and selected blood changes. Larvae penetrated the wall of the ileum, cecum and colon. The molt to the fourth stage occurred mostly in the wall of the ventral colon before 2 wk PI and larvae attained the liver mainly via the peritoneal cavity as early as eight days PI and persisted in the liver until 17 wk PI. Following active migration within the liver, invasion of the pancreas was accomplished at least by 7 wk PI with maximum numbers at 17 wk. The fourth molt occurred about 15 wk PI and preadults were present in the wall of the ventral colon at 30 wk PI and in the lumen of the colon at 40 wk. Strongylus equinus tends to wander retroperitoneally to the flanks, perirenal fat, diaphragm, omentum and occasionally to the lungs. Between 1 and 4 wk PI small raised hemorrhagic areas were present on the serosa of the ileum and colon. Small white foci on the surface of the liver at 1 wk PI were followed by tortuous tracks 3 wk later. Pathological changes in the pancreas were evident at three months PI and more severe by four months. Granulomas containing larvae were common in the flanks, diaphragm, omentum and occasionally beneath the pleura of the lungs. Clinical signs were correlated with invasion of the pancreas, the fourth molt, maximum globulin values and high eosinophil counts.

Evaluation of ivermectin against later fourth-stage Strongylus vulgaris in ponies at two and five weeks after treatment.

The efficacy of ivermectin against later fourth-stage Strongylus vulgaris larvae was studied in pony foals at 14 and 35 days after treatment. These foals had been reared parasite-free, inoculated with 500 infective larvae and 56 days later given either ivermectin at 200 micrograms/kg or a placebo intramuscularly. At necropsy, foals were examined for lesions and larvae grossly and histologically. Ivermectin was found to be highly effective (98.6%) against later fourth-stage larvae in five foals which were examined at 35 days after treatment, but not in five others examined at 14 days (72.5%). In some foals larvae were found in the tunica media of the ileocolic arteries. The conformation of these larvae appeared normal, but there were degenerative changes which suggested that they were dying or dead. Questions as to how the larvae attained that site and the consequences of their presence there were raised.

Effectiveness of fenbendazole against later 4th-stage Strongylus vulgaris in ponies.

Twelve pony foals (reared worm-free) were inoculated with Strongylus vulgaris. Approximately 8 weeks later, 4 of the foals were given fenbendazole (10% suspension) at a dosage rate of 10 mg/kg of body weight daily for 5 days and 4 foals were given the suspension at a dosage rate of 50 mg/kg daily for 3 days; the remaining foals were given a placebo. All treatments were administered by stomach tube. Fenbendazole was 99.6 and 97.9% effective in the 2 treatment groups, respectively, in eliminating later 4th-stage S vulgaris larvae located near the origin of major intestinal arteries. On microscopic examination of the ileocolic artery from fenbendazole-treated foals, a few larval remnants were found beneath the tunica intima in small organized mural thrombi overgrown with endothelium. It would appear that larvae are rapidly destroyed after administration of fenbendazole. A pony foal reared on pasture and with arteriographic evidence of arteritis of the cranial mesenteric and ileocolic arteries was treated with fenbendazole (10% suspension) by stomach tube at a dosage rate of 50 mg/kg of body weight daily for 3 days. By arteriographic examination made 4 weeks later, there was evidence of regression of the lesion, and at necropsy done a week later, there was no arteritis or larvae in the lumen of those arteries.

Effectiveness of ivermectin against later 4th-stage Strongylus vulgaris in ponies.

Twelve pony foals were reared worm-free and inoculated with Strongylus vulgaris. Approximately 8 weeks after they were inoculated, 6 foals were given ivermectin IM at a dosage rate of 200 micrograms/kg of body weight and 6 were given a placebo. All foals were necropsied 35 days after treatment. Ivermectin was 98.9% effective in eliminating later 4th-stage S vulgaris larvae located near the origin of major intestinal arteries and in reducing clinical signs and permitting resolution of lesions associated with verminous arteritis. One pony foal reared on pasture and with evidence of arteritis of the cranial mesenteric and ileocolic arteries on arteriography was treated with ivermectin at a dosage rate of 200 micrograms/kg of body weight. On arteriographs taken subsequently, there was evidence of regression of the lesion, and at necropsy 9 weeks after treatment, there was no arteritis or larvae in those arteries.

Controlled tests of fenbendazole against migrating Strongylus vulgaris in ponies.

Sixteen pony foals were reared worm-free and inoculated with Strongylus vulgaris. On day 7 after inoculation, 12 ponies were given a fenbendazole 10% suspension at dose rate of 50 mg/kg of body weight by stomach tube. On day 8 after inoculation, 8 of these ponies were given the 2nd treatment of the anthelmintic and on day 9, 4 of these ponies were given the 3rd treatment. (The other 4 of the 16 ponies were given only tap water, as controls.) The ponies were necropsied at death or on day 28 after inoculation. Fenbendazole was effective in minimizing the appearance of clinical signs associated with acute arteritis and was highly efficacious in eliminating early 4th-stage S vulgaris larvae in ponies treated for 3 consecutive days (ie, days 7, 8, and 9). After administration of the anthelmintic, clinical signs of toxicosis were not observed.

Controlled tests of ivermectin against migrating Strongylus vulgaris in ponies.

Twelve pony foals were reared worm-free and inoculated with Strongylus vulgaris. On day 7 after inoculation, 6 ponies were given ivermectin IM at a dose of 200 micrograms/kg of body weight and on day 28 were necropsied. Ivermectin was effective in eliminating early 4th-stage S vulgaris larvae and reducing clinical signs associated with acute arteritis. After administrative ivermectin was effective against early 4th-stage Strongylus vulgaris larvae in ponies when administered at 100, 300, or 800 micrograms/kg of body weight. The purpose of the present study was to report on a more extensive trial, using a single dosage of ivermectin.

Pathogenicity of immature Fascioloides magna in white-tailed deer.

The pathogenesis of early prepatent Fascioloides magna infection was investigated in seven fawns (Odocoileus virginianus) given 500 metacercariae and examined at one, two, three, five, eight, 12 and 13 weeks postinoculation. Blood samples were taken from eight inoculated deer every two weeks up to 16 weeks postinoculation. Eosinophilia with a mild transitory anemia were the main clincopathological features. Postmortem examination at two weeks postinoculation revealed extensive migration of immature flukes. Subcapsular tracks in the liver, nodules on the blind sacs of the rumen, as well as retroperitoneal granulomas on flanks and necrotic tracks on the diaphragm were found. Evidence of penetration of flukes into the lung was found at two weeks postinoculation and there was early granuloma formation at three weeks postinoculation. Flukes migrating into tissues other than the liver were destroyed in large granulomas, although remnants of degenerating parasites were not found. At eight weeks postinoculation, widespread granuloma formation characterized the infection with this lesion present in nodes along the gastrointestinal tract, in the mesentery, flanks, psoas muscles, diaphragm, between the ribs and in the lungs. By 12 weeks postinoculation subcapsular tracks were observed in the liver.

Evaluation of pyrantel pamoate, nitramisole and avermectin B1a against migrating Strongylus vulgaris larvae.

Trials were conducted in ponies to evaluate the efficacy of pyrantel pamoate (Strongid-T(R)) and two newer anthelmintics not yet commercially available, nitramisole and avermectin B(1)a, against migrating Strongylus vulgaris larvae. Ponies were removed from their mares within 24-48 hr after birth and reared in isolation, worm free. Between six and 14 weeks of age they were infected with 2000 or 2500 infective S. vulgaris larvae. Subsequently, they were monitored daily for clinical signs until the experiment terminated at 28 days postinfection. All ponies showed increased body temperature and reduced appetite within the first week of infection. All anthelmintics were administered on day 7 and in addition pyrantel pamoate was given on day 8 postinfection. The anthelmintics were in liquid formulation. Nitramisole and pyrantel pamoate were given by stomach tube and avermectin B(1)a by subcutaneous injection.Following administration of these compounds toxic reactions were not observed. All anthelmintics caused a reduction in body temperature and increased appetite and effected a clinical cure. In ponies which were not treated with an anthelmintic, temperatures remained elevated and appetites never returned completely to normal. These ponies also showed variable degrees of lethargy, depression, recumbency and colic and the majority died between two and three weeks postinfection. At necropsy, these control ponies showed variable degrees of adhesions involving the abdominal organs, necrosis of the ileum and cecum and severe arteritis and thrombosis of the major abdominal arteries and their branches.Although pyrantel pamoate, used at eight times the therapeutic dose for intestinal nematodes in the horse, effected a clinical cure it did not produce a radical cure. At necropsy, ponies treated with pyrantel pamoate had arteritis and thrombosis of the cranial mesenteric artery and its major branches. Nitramisole and avermectin B(1)a were able to effect both a clinical and radical cure.

Strongylus edentatus: development and lesions from ten weeks postinfection to patency.

Pony foals inoculated with infective Strongylus edentatus larvae were examined at necropsy from ten to 72 weeks postinfection. At ten weeks postinfection larvae were visible retroperitoneally in the liver and flanks and were recovered from the ligaments of the liver. The fourth molt was detected at 16 weeks postinfection and larvae were also recovered from the wall of the cecum at this time. By 40 weeks adult S. edentatus containing eggs were found in the contents of the cecum and colon. While many larvae migrate to remote parts of the body, it is likely that only those that attain the base of the cecum are successful in establishing in the cecum and colon as adult forms. By 36 weeks postinfection no larvae were found in the liver and up to this time none were found in the peritoneal cavity. Larvae were not recovered from the parenchyma of the lungs. Adhesions and disruption of omental architecture were frequent changes observed throughout infection. Casts of necrotic eosinophils enclosing tracks and larvae were observed beneath the intima of major veins of the cecum and colon. The liver was rough and the capsule thickened at 16 and 20 weeks postinfection and the flanks remained edematous until 36 weeks postinfection.

Changes in the generation cycle of duodenal crypt cells in chickens infected with Eimeria acervulina.

Changes in the duration of the progenitor cycle and its four phases were determined for duodenal crypt cells in chickens infected with Eimeria acervulina. Metaphase curves were constructed using percent labelled metaphase nuclei in duodenal crypt cells at short intervals after the injection of [3H]thymidine. The duration of the progenitor cycle and its four phases were calculated using the synthetic index and data obtained from the metaphase curves. The cycle time was reduced from 14 h in control birds to 10.2 h at 2 days and 10.6 h at 4 days postinfection. The change was attributable entirely to a reduction in G1 or the presynthetic phase. In addition, the population of dividing cells within each duodenal crypt was almost doubled in infected birds. These increases in cell production precedes all the histological changes observed earlier in the intestines of E. acervulina infected chickens. At least in this instance, changes in crypt morphology seems, therefore, to result from an induced change in the functional activity of the crypt.

Arteriography in ponies with Strongylus vulgaris arteritis.

Radiographs of the aorta and abdominal arteries were obtained from a normal anesthetized pony following catheterization of a femoral artery for nonselective, semiselective or selective arteriography. The arteries had smooth borders and regular diameters and the branches of the cranial mesenteric artery could be followed distally on the angiogram through to the smaller branches proximal to the bowel wall. Following arteriography, the pony walked normally and there were minimal alterations of the levels of serum muscle enzymes and blood lactate. The procedures for arteriography were repeated in three days. At that time the femoral artery was patent and satisfactory angiograms were obtained. Similiarly, radiographs were obtained from two ponies artificially infected with Strongylus vulgaris. The cranial msenteric artery and some of its branches, the right renal artery and segments of the aorta had irregular borders and were enlarged. Branches of the cranial mesenteric artery could not be followed distally because the flow of the contrast material was blocked. Following the above procedures, euthanasia of all ponies was expedited and the findings of arteritis, thrombosis and dilatation of arteries at necropsy compared favorably with interpretations from the radiographs. At least in the pony, arteriography can be a valuable research and diagnostic tool for the demonstration of lesions associated with verminous arteritis.

Protection by acetylsalicylic acid and other agents in experimental acute interstitial pneumonia of calves.

In experimental acute interstitial pneumonia caused by Ascaris suum, therapy with aspirin (acetylsalicylic acid) provided symptomatic control of the condition, reducing or abolishing the characteristic "setback". Treatment with antihistamines or antiserotonin agents caused no observable clinical improvements.

Suppression of the pathogenic effects of Strongylus edentatus larvae with thiabendazole.

Four pony foals were inoculated with Strongylus edentatus infective larvae and on days 3 and 4 postinfection two of the ponies were treated with thiabendazole, each at the rate of 440 mg/kg of body weight. Total circulating eosinophil counts in untreated ponies increased to over 1700 per cu mm after the second week postinfection. In the treated ponies as well as in an uninfected untreated pony eosinophil counts did not increase beyond 100 per cu mm. At necropsy on day 35 postinfection the cecum, colon and omentum of treated ponies were normal and few tracks were present on the surface of the liver. In untreated ponies nodules were observed on the serosal surface of the cecum and right ventral colon and white foci and tracks were numerous on the surface of the liver. A total of 53 fourth stage larvac was recovered from the livers of the thiabendazole treated ponies and 1194 from the untreated ones.