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1.
Sixteen 7-week-old Holstein male calves were inoculated with sporulated oocysts of Eimeria zuernii. Four calves (controls) were euthanatized and necropsied at 14 and 20 days after inoculation (DAI). Two calves were treated with 20 mg of dexamethasone (IM) on 13, 14, and 15 DAI and euthanatized and necropsied 17 DAI and 2 calves were given similar treatments and necropsied 20 DAI. The 8 other calves were euthanatized and necropsied 20 DAI. Two were started on the anticoccidial drug decoquinate in feed 13 DAI; 2 others were given decoquinate on the same schedule plus dexamethasone on 13,14, and 15 DAI. Two calves were given the antibiotic narasin in feed beginning 13 DAI and 2 calves were given parasin on the same schedule plus dexamethasone on 13,14, and 15 DAI. All calves, except 2 controls necropsied 14 DAI and 4 calves given decoquinate, discharged moderate-to-large numbers of oocysts in feces and had moderate-to-serve changes in fecal consistency. Histologic examinations revealed large numbers of endogenous stages in tissues of calves treated or not treated with dexamethasone. Few endogenous stages were observed in tissues from calves that were given decoquinate or decoquinate plus dexamethasone. Calves given narasin or narasin plus dexamethasone had moderate-to-large numbers of endogenous stages in the tissues.  相似文献   

2.
Two experiments were conducted to evaluate lasalocid as a coccidiostat in Holstein calves and to compare lasalocid with monensin and decoquinate. In experiment 1, calves in 3 groups (6 calves/group) were each inoculated with 500,000 sporulated oocysts, 88% of which were Eimeria bovis and 12% were E zuernii. Calves in each group were given lasalocid-medicated feed at 0.50 (group 3), 0.75 (group 4), or 1 mg/kg (group 5) of body weight/day for 45 days. Two control groups (6 calves/group) were also evaluated; calves in control group 2 were inoculated and nontreated, and calves in control group 1 were noninoculated and nontreated. At 0.50, 0.75, or 1 mg/kg/day, lasalocid was equally effective in preventing induced coccidiosis (E bovis and E zuernii) in calves. Compared with inoculated nontreated controls, treated calves had significantly (P less than 0.05) fewer oocysts in feces and had fewer clinical signs of coccidiosis from days 16 to 30 after inoculation. Experiment 2 was conducted to compare the effectiveness of monensin, lasalocid, and decoquinate for the prevention of experimentally induced coccidiosis. Calves (n = 48) were allotted into 4 groups (12 calves/group); each was inoculated orally with 275,000 sporulated oocysts, predominantly E bovis and E zuernii, and each was given nonmedicated feed (group 6) or feed medicated with 33 mg of lasalocid (group 7), decoquinate (group 8), or monensin (group 9)/kg of feed for 46 days. Calves given medicated rations had significantly (P less than 0.05) fewer oocysts in their feces and fewer clinical signs of coccidiosis than did calves given nonmedicated rations.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

3.
Newborn Holstein male calves were purchased within 3 days after birth and were removed from the local farms to the Dixon Springs Agricultural Research Center. They were hand-fed for 7 weeks and then weaned to a prepared feed. Eight groups, each of 4 calves, were housed in separate pens. In each of 4 pens (pens 2 to 5), 1 calf was inoculated with sporulated oocysts of Eimeria bovis (and was not medicated); 1 calf was inoculated and given feed with added monensin at the dosage level of 10 g/906 kg of feed; and 2 calves were inoculated and given medicated feed with added monensin at the dosage level of 20 g/906 kg or 30 g/906 kg. In the 4 other pens (6 to 9), the calves were inoculated with E zuernii and otherwise were given feed without or with added monensin as in pens 2 through 5. Another group of 5 calves (all kept in 1 pen), served as noninoculated, nonmedicated controls. At 14 days after inoculations with E bovis, the single calves in each of the 4 pens that were given the nonmedicated feed began to show clinical signs of coccidiosis and discharged increasing numbers of oocysts. The other inoculated calves (given monensin) had fewer clinical signs and discharged fewer oocysts in the feces as the level of medication in the feed increased. The calves inoculated with E zuernii developed only moderately severe infections when compared with those inoculated with E bovis. Inoculated (with E bovis) nonmedicated calves had severe reductions in feed consumption and weight, and 3 of 4 died.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

4.
Coccidiosis due to an Isospora ohioensis-like organism was diagnosed in a 10-week-old pup. The pup had diarrhea, dehydration, and weight loss before it died 7 days after onset of clinical signs. Lesions were limited to the intestinal tract. Beginning in the distal end of the small intestine and extending through cecum and colon were mild histiocytic proliferation in the lamina propria and multifocal cryptitis. Numerous meronts and gamonts of an unidentified coccidium were in or near the lesions. Parasites were in the villous epithelium, lamina propria, and intestinal glands of the distal one-half of the small intestine, cecum, and colon. It was concluded that infection was due to an unidentified coccidium with oocysts structurally similar to those of I ohioensis.  相似文献   

5.
Exogenous and endogenous stages of Isospora burrowsi n sp from the dog are described. Oocysts were spherical or ellipisoidal and 17 to 22 by 16 to 19 micrometer (mean 20.3 by 17.3 micrometer). Micropyle, oocyst residuum, and polar granule were not present. Sporocysts were 12 to 16 by 8 to 11 micrometer (mean 14.4 by 9.7 micrometer). Stieda body was absent, but a sporocyst residuum was present. Endogenous stages were in the caudal three-fifths of the small intestine and in the cecum. Mature 1st-generation schizonts (11 to 18 by 9 to 18 micrometer) were present on the 4th day of infection. One day later, mature 2nd-generation schizonts (18 to 35 by 17 to 22 micrometer) were present. Immature gamonts were found 5 days after infection, and unsporulated oocysts were also present later that day. The prepatent period was 6 days, and the mean patent period was 11 days. The oocysts of I burrowsi differ markedly in size from all other Isospora species from dogs, except Isospora ohioensis; however, the endogenous stages of the 2 species differ.  相似文献   

6.
Twenty coccidia-free Holstein bull calves were allotted to groups to study effects of treatment with lasalocid and decoquinate on subsequent resistance to coccidiosis (Eimeria spp infections). Calves fed medicated rations of either drug at dosages of 50 mg/kg of feed (approx 1.2 mg/kg of body weight) had significantly fewer oocysts (P less than 0.01) than did nontreated controls regardless of other procedures used. Treated calves premunized with 2,000 oocysts/day for 5 days and later challenge inoculated with 200,000 oocysts did not develop diarrhea, unless the drugs were withdrawn from feed. Animals premunized (2,000 oocysts/day for 5 days) in absence of drug were no more resistant to the challenge inoculation than nonpremunized animals. These results indicated that lasalocid and decoquinate were efficacious coccidiostats and protected calves as long as they were administered. Cessation of drug treatment usually resulted in appearance of oocysts in feces and diarrhea. Premunization alone cannot be expected to prevent coccidiosis when animals are exposed to large numbers of oocysts.  相似文献   

7.
Donor chickens given feed medicated with one or two levels of decoquinate or given non-medicated feed were infected with oocysts of Eimeria tenella or E. maxima per os. Twelve hours after inoculation with oocysts liver, mid-intestine or ceca homogenates were fed to previously uninfected recipient chickens. The results showed that continuous medication with decoquinate was effective in preventing the transfer of sporozoites from the intestine to the liver. Oocysts were detected in the feces of all recipients of tissue from non-medicated donors, showing that some sporozoites of E. maxima and E. tenella are normally transferred to liver. Young broiler chickens were immunized by oral inoculation of E. maxima oocysts. The immune status of similar chickens inoculated with sporozoites of the same species directly into the liver or spleen were assessed. During the experimental period half of the chicks were provided with non-medicated food and the remainder were given feed supplemented with decoquinate; decoquinate was effective in arresting the development of the sporozoites. Two weeks after initial infection the birds were challenged with oocysts of E. maxima per os. Injection of sporozoites into the spleen did not protect against challenge. Birds inoculated with sporozoites into the liver were unable to develop a significant level of immunity. When the drug pressure was removed from these birds, parasitism of the intestine occurred and immunity developed.  相似文献   

8.
Broiler chickens in battery pens were either fed a diet containing 100 ppm lasalocid or no drug for 24 h prior to inoculation with sporulated oocysts of Eimeria tenella or Eimeria acervulina. Different groups of birds remained on medicated feed for 24, 48, 72, 96, 120 or 144 h after inoculation. Conversely, other groups started on an unmedicated diet, were given medicated feed at different times after oocyst inoculation. Starting lasalocid medication 24 h (E. tenella) or 48 h (E. acervulina) after inoculation reduced the lesions and improved the weight gain. There was no significant difference in performance of birds after withdrawal of the drug at 48 h (E. tenella) or 72 h (E. acervulina) and thereafter. Starting lasalocid medication at 96 or 120 h did not suppress but rather reduced oocyst production.  相似文献   

9.
杀球灵对柔嫩艾美耳球虫作用的研究   总被引：3，自引：0，他引：3  
本文报道了杀球灵(Diclazuril)对鸡柔嫩艾美耳球虫E.tenella的杀灭作用、作用峰期及停药后作用持续时间。以1ppm的推荐剂量混于饲料,分别于感染前2天、感染当天、感染后1天开始饲喂,对经口一次人工感染8×10~4/只柔嫩艾美耳球虫卵囊的鸡有显著的保护作用。试验鸡不出现血便、盲肠组织学检查及粘膜刮取物镜检均不见合子及卵囊,感染后2天给药则其抗球虫作用显著降低。故可认为杀球灵作用峰期是子孢子和第一代裂殖体阶段。停药后其抗球虫作用很快减弱或消失。  相似文献   

10.
An experiment was conducted to reproduce respiratory tract disease with bovine respiratory syncytial virus (BRSV) in one-month-old, colostrum-fed calves. The hypothesized role of viral hypersensitivity and persistent infection in the pathogenesis of BRSV pneumonia was also investigated. For BRSV inoculation a field isolate of BRSV, at the fifth passage level in cell culture, was administered by a combined respiratory tract route (intranasal and intratracheal) for four consecutive days. Four groups of calves were utilized as follows: Group I, 6 calves sham inoculated with uninfected tissue culture fluid and necropsied 21 days after the last inoculation; Group II, 6 calves inoculated with BRSV and necropsied at the time of maximal clinical response (4-6 days after the last inoculation); Group III, 6 calves inoculated with BRSV and necropsied at 21 days after the last inoculation; Group IV, 6 calves inoculated with BRSV, rechallenged with BRSV 10 days after initial exposure, and necropsied at 21 days after the initial inoculation. Clinical response was evaluated by daily monitoring of body temperature, heart rate, respiratory rate, arterial blood gas tensions, hematocrit, total protein, white blood cell count, and fibrinogen. Calves were necropsied and pulmonary surface lesions were quantitated by computer digitization. Viral pneumonia was reporduced in each principal group. Lesions were most extensive in Group II. Disease was not apparent in Group I (controls). Significant differences (p less than 0.05) in body temperature, heart rate, respiratory rate, arterial oxygen tension, and pneumonic surface area were demonstrated between control and infected calves. Results indicate that severe disease and lesions can be induced by BRSV in one-month-old calves that were colostrum-fed and seropositive to BRSV. BRSV rechallenge had minimal effect on disease progression. Based on clinical and pathological response, results did not support viral hypersensitivity or persistent infection as pathogenetic mechanisms of BRSV pneumonia.  相似文献   

11.
Lesions of sarcocystosis were studied in 14 calves necropsied between seven and 110 days after inoculation with 5000 to 25 million sporocysts of Sarcocystis hirsuta from cats. Calves developed fever, anemia, and diarrhea between 11 and 30 days after inoculation. The development of first generation meronts in arteries of small intestine, mesentery, and mesenteric lymph nodes seven to 25 days after inoculation was associated with vascular occlusion and necrosis of associated tissues. The development of second generation meronts in capillaries of striated muscles 15 to 23 days after inoculation was associated with necrosis, edema, and nonsuppurative myositis in heart and other muscles. Sixty-two days after inoculation lesions were reduced to focal areas of granulomatous inflammation around degenerating sarcocysts in striated muscles, but not in the heart.  相似文献   

12.
Male Holstein calves were each inoculated with 350,000 sporulated oocysts of Eimeria bovis. Two calves were given decoquinate (0.5 mg/kg of body weight) continuously in dry feed for 29 days, and 2 calves each were given 0.5, 1, or 1.5 mg of decoquinate/kg on an every 2nd-or 3rd-day schedule for 29 days. Calves given decoquinate continuously did not discharge oocysts but had slightly loose feces. In general, the number of oocysts discharged increased and fecal consistency decreased as the time between feeding of medicated feed increased. Calves given 0.5 or 1.5 mg of decoquinate/kg every 3rd day discharged more oocysts and had more diarrhea than did calves given 1 mg of decoquinate/kg every 3rd day. At postinoculation day 29, calves were euthanatized. At necropsy, intestinal tissues of calves given decoquinate were mostly normal. Apparently, reduced infections along with the elapsed time were sufficient to resolve most intestinal lesions caused by the coccidia. Decoquinate was most effective when fed continuously at 0.5 mg/kg. However, when fed at 1 or 1.5 mg of decoquinate/kg every 2nd day or 1.5 mg of decoquinate/kg every 3rd day, oocyst production was reduced and clinical coccidiosis was prevented.  相似文献   

13.
Fifteen weaned calves (age 89-141 days) were treated with dexamethasone (0.25 mg/kg, IV) for 3 days before, the day of, and the day after inoculation with 10 colony-forming units of either Escherichia coli O157:H7 (strain 86-24, which produces Shiga toxin 2 and intimin; n = 13) or nonpathogenic E. coli (strain 123, which does not produce Shiga toxin or intimin; n = 2). All calves were necropsied 4 days after inoculation. Histologic lesions of attaching and effacing bacteria were observed in the large intestine (12/13) and in the gallbladder mucosa (5/13) of calves inoculated with E. coli 86-24. Cholecystitis was present in 12 of 13 calves that received E. coli 86-24. Inoculum bacteria were recovered from the distal colons or feces (13/13) and gallbladders (3/4) of calves inoculated with 86-24.  相似文献   

14.
Eight female, 12- to 34-month-old, specific-pathogen free cats were inoculated orally with Toxoplasma gondii cysts on day 0, then with Isospora felis and Isospora rivolta oocysts on day 39, and cysts of Hammondia hammondi on day 86 after inoculation with Toxoplasma. All cats shed oocysts of all 4 of these coccidia within 11 postinoculation days. The female cats were caged with 4 male Toxoplasma-free cats, starting 66 days after inoculation with Toxoplasma, until they were 5 to 6 weeks pregnant. Kittens that were born were housed with their mothers until necropsied or weaned. One 42-day-old kitten shed T gondii oocysts in feces. It was necropsied 2 days later and asexual stages of Toxoplasma (types D and E), gametocytes, and oocysts were demonstrated in sections of superficial epithelial cells of its small intestine. Lesions or forms of Toxoplasma were not demonstrated histologically in tis extraintestinal organs. Toxoplasma was not isolated from feces or tissues of the remaining 47 kittens born to these 8 queens. Toxoplasma was not isolated from the 4 male cats that were caged with infected females for 53, 59, 217, and 217 days. The source of toxoplasma infection in the kitten remained unknown but was considered unlikely to be congenital or through fecal contamination. Oocysts of I felis, I rivolta, and H hammondi were not found in the feces of any kittens, indicating that these coccidia are unlikely to be transmitted congenitally.  相似文献   

15.
Two studies were performed to examine the efficacy of milbemycin oxime against fourth-stage larvae or adults of Toxocara cati. In the study to determine efficacy against fourth-stage larvae, 20 domestic shorthair cats were inoculated with 500 embryonated eggs. Four weeks after inoculation, the animals were allocated to two groups, and cats in one group were treated with medicated tablets containing 4 mg milbemycin oxime and 10mg praziquantel (MILBEMAX) and cats in the other group with placebo tablets. Seven days after treatment the animals were euthanatized and necropsied for worm counting. The number of worms found was significantly (p=0.0002) lower in cats treated with medicated tablets than in cats treated with placebo tablets. The reduction in the number of worms was 96.53%. In the study to determine efficacy against mature adult worms, 13 kittens were inoculated with T. cati embryonated eggs. On day 45 after inoculation and after the infection had been confirmed through faecal examinations for 11 out of the 13 animals, the 11 infected animals were allocated to two groups and treated as in the first study. Seven days after treatment, all animals were euthanatized and necropsied for worm counting. The number of worms found was significantly (p=0.0043) lower in kittens treated with medicated tablets than in kittens treated with placebo tablets. The reduction in the number of worms was 95.90%. No adverse effects were recorded during either study. It is concluded that the milbemycin oxime-praziquantel tablets that were used are efficacious for the control of T. cati infections in cats.  相似文献   

16.
The development of pathological lesions in the small intestine of neonatal calves is described. Seven newborn calves were challenged orally with a known enteropathogenic strain of E coli 0101k?(A) and killed at varying times after inoculation. Adhesion of bacteria to the mucosa of the small intestine was observed in all calves. A few organisms were seen in the distal small intestine at three hours after inoculation and thereafter adhesion progressed anteriorly along the intestine in calves killed from six to 36 hours. In these calves pathological changes occurred between six and 12 hours after inoculation. Villi were stunted and thickened and the epithelial surface was irregular. A further calf, anaesthetised from five-and-a-half to 10 hours after inoculation and repeatedly sampled from the distal small intestine, developed similar lesions abruptly at nine hours after inoculation. Villus and crypt lengths in the challenged calves were compared with those in three normal uninoculated control calves.  相似文献   

17.
31 to 37 localities were examined in the small and large intestines of 48 calves spontaneously infected with cryptosporidiosis. It was found that cryptosporidia occurred the most frequently in the distal part of small intestine, within the range of six metres of small intestine, in front of the ostium ileocecale (OIC); at the ileocecal valve the incidence of cryptosporidia dropped rapidly. In none case were the protozoans revealed in duodenum and in the adjacent four to six metres of proximal jejunum. The small intestine was invaded by cryptosporidia in a variable manner, in some cases a major part was continuously invaded, in other cases only one or two metres of distal jejunum without any changes in the ileum and vice versa. Approximately half the calves had cryptosporidia in the cecum, fewer cryptosporidia were found in the transverse colon. Cryptosporidia in the rectum were found in about 25% of cases. Some calves had cryptosporidia only in the large intestine. The intensity of the mucous membrane invasion varied: mass incidence of cryptosporidia was found only in caudal parts of small intestine, with high variability of the extent and with sudden cases of negative findings. In the large intestine only the cecum was invaded more intensively and in a diffusive manner, in the transverse colon and in the rectum the groups of parasites were usually found at the openings and in the wall of Lieberk uhn 's crypts.  相似文献   

18.
Performance and ruminal changes of early-weaned calves fed lasalocid   总被引：1，自引：0，他引：1  
Twenty-two neonatal calves were assigned to a control or lasalocid-fed group and weaned at 3 wk of age. They were fed a prestarter diet from 3 d of age until they consumed 227 g/d and then a mixture of 227 g prestarter daily and starter diet in ad libitum amounts. The lasalocid-fed group received lasalocid in milk at 1 mg/kg body weight daily from 4 to 7 d and at .5 mg/kg body weight daily in milk and medicated prestarter diet (88 mg lasalocid/kg) during the 2nd wk. After 2 wk, lasalocid-fed calves were given medicated prestarter and starter (44 mg lasalocid/kg) diets. Four calves in each group were ruminally cannulated at 3 to 5 d of age, and ruminal contents were obtained at weekly intervals to monitor microbial activity. Rectal fecal samples were collected from all calves and examined for coccidial oocysts. Lasalocid-fed calves had a greater weekly feed intake and weight gain than control calves after 6 wk of age. Total ruminal volatile fatty acid concentrations were higher, but the acetate:propionate ratio was lower in lasalocid-fed calves than in control calves. Total viable anaerobic and amylolytic bacterial counts were higher in lasalocid-fed calves than in control calves. No significant treatment effect was found for ruminal NH3-N concentration or ruminal lasalocid-resistant, lactobacilli, lactate-utilizing, cellulolytic or methanogenic bacterial numbers. No evidence of coccidiosis was detected in either group. In general, lasalocid-fed calves had greater feed intake, weight gain and ruminal microbial activity than the calves fed no lasalocid in the diet.  相似文献   

19.
This study was undertaken to determine if administration of recombinant bovine interleukin-12 (rBoIL-12) could stimulate a cellular immune response that protected calves from an oral challenge inoculation with Cryptosporidium parvum oocysts. In a first experiment, rBoIL-12 intraperitoneally administered as a single dose 1 day before challenge inoculation, did not alter the course of infection. The percentage of immune competent cells and levels of cytokine gene expression in the ileo-cecal mucosa and in the draining lymph nodes of treated calves were similar to those of untreated control calves. However, when rBoIL-12 was subcutaneously administered daily from 2 days before infection to 2 days after infection, a consistent increase of T lymphocytes and an higher expression of interferon-gamma (IFN-gamma) was detected. Again, treatment did not alter the course of infection. Similar results were obtained when rBoIL-12 was administered daily for 4 days beginning 2 days after oral inoculation. These data indicate that although rBoIL-12 stimulated a strong immune response in the gut of neonatal calves, the response was not able to provide protection from challenge inoculation with C. parvum oocysts.  相似文献   

20.
An isolate of Eimeria meleagridis Tyzzer, 1927 was obtained by harvesting oocysts from the ceca of a turkey from northwest Arkansas and a pure line was established by infecting birds with a single oocyst. Oocysts were first produced in the ceca of infected birds from 102 to 108 hr after inoculation and were of similar size (mean length X width, 24.9 X 17.0 microm) to those of Eimeria adenoeides Moore and Brown, 1951 and Eimeria gallopavonis Hawkins, 1952. The line was identified as E. meleagridis based upon the development of large schizonts in the midintestine, and small schizonts in the ceca. Two generations of large schizonts were found 48 and 72 hr after infection, and at least two generations of small schizonts were found from 60 to 108 hr after infection. An inoculum of 2 X 10(5) oocysts was found to cause a significant reduction in weight gain from days 0-3 and 0-6 after infection, suggesting that the significance of this species of Eimeria as a pathogen of turkeys should be reassessed.  相似文献   

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