Porcine neonatal coccidiosis: evaluation of monensin as preventive therapy

In this study, we evaluated the efficacy of monensin as a preventive therapy for porcine neonatal coccidiosis. Fifteen three-day-old piglets were given 50,000 sporulated oocysts of Isospora suis and eight of them received 15 mg/kg of monensin orally every other day. Seven piglets served as normal controls. Fecal samples were collected and checked for oocyst shedding. At 18 days of age, piglets were euthanized and necropsied.

The onset of clinical signs was delayed in the treated group, but all inoculated piglets displayed anorexia, soft stool, or diarrheic feces. Treated piglets shed large numbers of oocysts in their feces (up to 201,200 oocysts per gram of feces). All infected piglets had lesions of villous atrophy in the jejunum and most of them were in the late atrophic or villous regrowth stages.

The results of this study suggest that monensin does not prevent clinical signs, oocyst shedding, and intestinal lesions caused by I. suis in neonatal piglets.

     

Amprolium and furazolidone as preventive treatment for intestinal coccidiosis of piglets

Two coccidiostats, amprolium and furazolidone, were used as preventive treatments for intestinal coccidiosis in three-day-old piglets experimentally infected with 50,000 sporulated oocysts of Isospora suis.

All infected piglets, treated or not, displayed clinical signs compatible with coccidiosis. Diarrhea and anorexia appeared around five days postinoculation in the non-treated and in the amprolium-treated groups; these signs were delayed to days 7 and 8 postinoculation in the furazolidone-treated group. The treatments did not prevent growth retardation. Amprolium seemed to reduce oocyst shedding whereas furazolidone had no effect. Villous atrophy was present in all infected piglets.

     

Experimental infection of dogs (Canis familiaris) with sporulated oocysts of Neospora caninum

Neospora caninum is widely distributed in the world and this parasite is one of the major causes of abortion in cattle. Dogs and coyotes are definitive hosts of N. caninum and several species of domestic and wild animals are intermediate hosts. Dogs can become infected by the ingestion of tissues containing cysts and then excrete oocysts. It is not yet known whether sporulated oocysts are able to induce a patent infection in dogs, i.e. a shedding of N. caninum oocysts in feces. The objective of this study was to experimentally examine the infection of dogs by sporulated oocysts. The oocysts used in the experiment were obtained by feeding dogs with brain of buffaloes (Bubalus bubalis) positive for anti-N. caninum antibodies by indirect fluorescent antibody test (IFAT ≥200). Oocysts shed by these dogs were confirmed to be N. caninum by molecular methods and by bioassay in gerbils, and sporulated N. caninum oocysts were used for the oral infection of four dogs. The dogs were 8 weeks old and negative for antibodies to N. caninum and Toxoplasma gondii. Dogs 1 and 4 received an inoculum of 10,000 sporulated oocysts each; dog 2 an inoculum of 5000 sporulated oocysts and dog 3 received 1000 sporulated oocysts of N. caninum. The total feces excreted by these dogs were collected and examined daily for a period of 30 days. No oocysts were found in their feces. The dogs were monitored monthly for a 6-month period to observe a possible seroconversion and when this occurred the animals were eliminated from the experiment. Dogs 1 and 4 seroconverted 1 month after the infection with titer, in the IFAT, of 1600 and 800, respectively; the other two dogs presented no seroconvertion during the 6-month period. Dogs 1 and 2 were euthanized 180 days after infection and were examined for the detection of N. caninum in tissues (brain, muscle, lymph node, liver, lung, heart and bone marrow) by immunohistochemistry and PCR with negative results in both techniques. Bioassay in gerbils with brain of these dogs was also performed and again the results were negative. In conclusion, dogs infected with sporulated oocysts of N. caninum were not able to shed oocysts in feces. However, a higher dose of infection stimulated the production of antibodies against N. caninum in the dogs.     

Possibilities of bacteremia and toxemia in death of chickens infected with Eimeria tenella

The possibility that bacteremia and toxemia were the causes of death in cases of cecal coccidiosis was investigated. Germ-free and ordinary chickens with microflora were inoculated with sporulated oocysts of Eimeria tenella. At 5 days postinoculation, cecal lesions in ordinary chickens were more severe than those in germ-free ones. Cardiac blood, spleen, and liver were examined in ordinary chickens for bacteremia and endotoxemia, and small numbers of bacteria were recovered from both infected and uninfected birds. Endotoxin levels in plasma of E. tenella-infected birds were low and not different from the levels of uninfected controls. To examine unknown toxic factors, a large volume of serum from infected chickens was injected intravenously into uninfected birds. No significant clinical signs were observed. It is concluded that the intestinal bacteria increase the severity of coccidial lesions without bacteremia and toxemia.     

Pathogenesis of intestinal cryptosporidiosis in conventional and gnotobiotic piglets.

The pathogenesis of intestinal cryptosporidiosis was studied in 52 conventionally reared and 20 gnotobiotically reared piglets by inoculation with different doses of Cryptosporidium parvum oocysts. The prepatent period of C. parvum in both groups of animals were variable, depending on the number of oocysts administered. The patent period of C. parvum in conventionally reared piglets was 8 or 9 days; in gnotobiotic piglets cryptosporidia were found in feces until Day post infection (DPI) 16, when the last piglet was necropsied. Cryptosporidiosis in conventionally reared piglets is a self-limited diarrheal disease associated with morphological changes within the intestine. The most severe lesion was seen in the posterior jejunum and ileum from DPI 3 to DPI 7, and consisted of villous atrophy, crypt hyperplasia and inflammatory infiltration in the lamina propria. In gnotobiotic piglets cryptosporidia induced severe enterocolitis which occurred at least until DPI 16. The characteristics of enteric lesions were similar to those found in conventionally reared piglets. Intestinal cryptosporidiosis in both groups of animals shifted in the course of infection in the caudal direction and terminated in the large intestine. Examination by scanning electron microscope showed that infected absorptive cells had thicker and longer microvilli than those on non-infected cells; neighboring non-infected cells were hypertrophic, bulbously protuberant with minute microvilli with no distinct intercellular borders. Numerous cryptosporidia in the heterotopic glandular epithelium in the submucosa of cecum and colon on DPI 9 and 10 were found. No differences in the location and degree of cryptosporidial infection between colostrum-fed and colostrum-deprived conventionally reared piglets were found. Sow's colostrum does not appear to protect piglets from C. parvum infection. The role of intestinal microflora in the pathogenesis of cryptosporidiosis in piglets is discussed.     

Experimental Klebsiella and Salmonella infection in neonatal swine.

Twenty colostrum-fed piglets from three sows were separated from the sows 24 hours after birth and were randomly divided into five groups of four piglets each. Every piglet in each of four test groups was orally inoculated with about 10(10) colony forming units of Salmonella typhimurium, Salmonella choleraesuis var Kunzendorf or one of two isolates of Klebsiella pneumoniae. One group served as uninoculated controls. Piglets infected with K. pneumoniae developed severe diarrhea beginning about 12 hours after inoculation. They became dehydrated and weak but continued to drink. There were no morphological alterations in intestinal mucosa when piglets were killed and necropsied 48 or 72 hours after inoculation. Klebseilla pneumoniae was isolated from intestine and feces but not from liver or spleen. Piglets inoculated with S. choleraesuis became lethargic and disinterested in food by 24 hours after inoculation. Diarrhea developed by 48 hours after inoculation. Lesions at necropsy 60 or 72 hours postinoculation were subcutaneous edema, mesenteric lymphadenitis, diffuse intestinal superficial mucosal necrosis with villous atrophy, and focal deep ulceration in the ileum. Salmonella choleraesuis was isolated from all segments of intestine and from feces, liver and spleen. Piglets inoculated with S. typhimurium developed a relatively mild diarrheal disease with lesions similar to those with S. choleraesuis infection but less severe. The inoculated organism was recovered from all areas of intestine and from feces, liver and spleen. Serum from infected and control piglets had high (greater than 1:256) agglutinating titres against S. typhimurium but low titres (0 to 1:8) against S. choleraesuis. The agglutinins were assumed to originate from colostral antibodies.     

Porcine Neonatal Coccidiosis

Coccidia were identified in intestinal sections from 82 piglets comprising 37 consignments from 34 farms, and represented a yearly increasing incidence in the three years 1978 to 1980. Piglets were primarily from medium to large farms with intensive, continuous-farrowing, confinement-rearing programs. Piglets, usually five days to 15 days old, had yellow, fluid diarrhea, became unthrifty and sometimes died. In six piglets from two farms, a green, adherent, fibrinonecrotic membrane was seen throughout most of the jejunum and ileum. Significant gross lesions were not observed in the other 76 piglets. Moderate to severe villous atrophy of jejunum and ileum was seen histologically. Various asexual and sexual stages of coccidia were seen within parasitophorous vacuoles of villar epithelial cells. Multifocal erosions with necrosis of villar tips and occasionally more diffuse mucosal necrosis with fibrinocellular exudate were seen. Isospora suis oocysts were identified in feces from several weaners from one farm. Amprolium and decoquinate mixed in the sow ration at 1 kg/tonne for three weeks prior to and postfarrowing was moderately successful in stopping outbreaks of neonatal diarrhea associated with coccidiosis.     

和缓艾美耳球虫致病性研究

对新分离的和缓艾美耳球虫进行了致病性研究.结果表明,21日龄雏鸡感染1000个和5000个孢子化卵囊未见异常表现,肠道未发现肉眼可见的病理变化.20 000个卵囊感染可引起轻微病变,100 000个和500 000个卵囊感染能产生较明显的致病作用,与对照组相比增重分别为70.3%和56.8%.根据肠道病变记分标准,肠道有明显可见的病变,所有试验鸡均未出现死亡.     

柔嫩艾美耳球虫早熟株免疫剂量研究

为了确定柔嫩艾美耳球虫（Eimenatenella）早熟株合适的免疫剂量,本文设立7个早熟株免疫攻虫组、1个不免疫攻虫组和1个不免疫不攻虫组,免疫组的免疫剂量为孢子化卵囊100、200、400、600、800、1000和2000个／羽,经嗉囊感染,7日龄首次免疫,14日龄以同等剂量进行第二次免疫,21日龄以8×10^4个／羽的同源母株进行攻虫,28日龄结束试验,以存活率、增重、肠道病变记分、血便数量、卵囊减少率为观测指标。对免疫保护效果较好的3个免疫剂量进行重复试验,同时设置商品化球虫疫苗对照组,免疫方法、试验周期、试验指标同第一批试验。结果显示：攻虫后,不免疫攻虫组出现5％死亡,而各免疫组来出现死亡;各免疫组卵囊减少率在61．57％～69．52％;200～2000免疫组的增重与不免疫不攻虫组差异不具备显著统计学意义（P〉0．05）;600～2000免疫组的肠道病变记分和血便数量均明显少于不免疫攻虫组（P〈0．05）。用600、800和1000进行重复试验,三个免疫组攻虫期间均来出现死亡,而不免疫组和疫苗对照组均出现5％死亡;三个免疫组的增重均明显高于不免疫攻虫组和疫苗对照组（P〈0．05）;早熟株免疫组的肠道病变记分和血便数量明显低于不免疫攻虫组（P〈0．05）,而疫苗对照组与不免疫攻虫组的相当（P〉0．05）;卵囊减少率在66.30％-78．75％,高于疫苗对照组的51．82％。结果表明,该柔嫩艾美耳球虫早熟株保持了良好的免疫原性,不同免疫剂量均能诱发鸡产生免疫保护力,其中600、800和1000个／羽的免疫效果均优于疫苗对照组,可考虑以600个／羽作为该早熟株在疫苗制备中的推荐免疫剂量。     

Shedding of Oocysts in Piglets Experimentally Infected with Isospora suis

Christensen, S. AA. Henriksen: Shedding of oocysts in piglets experimentally infected with Isospora suis. Acta vet scand., 1994, 35, 165-172.–Forty-seven piglets were inoculated with doses of 100 to 50,000 sporulated oocysts of Isospora suis. After 5-7 days oocysts were found in faeces. The patent period extended from 8 to 16 days. The shedding of oocysts showed a cyclic pattern with 2-3 peaks separated by intervals of approximately 5 days. Subpatent periods were often seen between the peaks.The level of oocyst shedding during the initial days of the patent period reflected, to some extent, the inoculation dose. However, a maximum of OPG at the 100,000 level was observed among one or more piglets from all groups, regardless of the inoculation dose. Among the majority of piglets inoculated with more than 100 oocysts, the highest OPG-figures were observed in the first peak of the cyclic pattern. Unlike this, the maximum of OPG was observed in the second peak of the cycle among 6 of the 7 piglets inoculated with 100 oocysts only. The triphasic pattern was most pronounced in the low dosed group.The marked upscaling of oocyst production, as particularly registered in the low dosed groups, seams to explain at least part of the problems met under practical conditions, when trying to eliminate the transmission of oocysts between successive litters in the farrowing boxes.The cyclic excretion pattern and an apparent absence of autoinfections may indicate that the development of I. suis in the host includes several oocyst producing generations descending from the same initial infection.The presence of subpatent periods can probably explain the marked variation in OPG, as they are often recorded when examining faecal samples from piglets, even when the samples are originating from the same litter.     

Natural transmission of group A rotavirus within a pig population

Five litters of piglets born within two days of each other, together with their dams, were investigated for faecal excretion of group A rotavirus antigen from birth to two months old. All the 50 piglets in these litters became infected with the virus between 19 and 35 days old. Rotavirus excretion was first seen in one litter which was housed with other litters not included in this study. Two days later, piglets of the second litter in another farrowing room began to excrete rotavirus, and then infection spread to the other three litters in the same room. Within each of these litters, one or two piglets were infected early and thereafter infection spread to other piglets. It took four to 10 days for rotavirus to infect every piglet within a litter, and 16 days in total before all piglets in the five litters were infected. No rotavirus antigen was demonstrated in faeces from sows during the investigation period.     

Experimental Eimeria debliecki infections in nursing and weaned pigs

Three litters of six, 3-day-old nursing pigs were inoculated via a stomach tube with 8.0 X 10(5), 1.6 X 10(6) or 5.0 X 10(6) sporulated oocysts of Eimeria debliecki and four groups of six, 4-week-old weaned pigs were inoculated with 8.0 X 10(5), 1.6 X 10(6), 5.0 X 10(6) or 1.0 X 10(7) sporulated oocysts of E. debliecki to determine its pathogenicity. Clinical coccidiosis or deaths did not result from infections. Infections were confined to the jejunum and occasionally the duodenum. Microscopic lesions of mild to moderate villous atrophy were observed in one nursing pig given 5.0 X 10(6) oocysts and three weaned pigs given 1.6 X 10(6), 5.0 X 10(6) and 1.0 X 10(7) oocysts and examined 5 days post-inoculation. Pathogenic bacteria or viruses were not demonstrated in any pigs. Results of this study indicate that E. debliecki is not a cause of neonatal or weaning diarrhea in pigs.     

Densitometric analysis of aminopeptidase M activity in small intestine mucosa in piglets experimentally infected with Isospora suis

In gnotobiotical and conventional piglets infected a day post partum (DPP) with oocysts of the coccidium Isospora suis, densitometrical analysis of the activity of aminopeptidase M (EC.3.4.11.2; APM) was performed in the area of microvillous zone of the small intestine. Piglets were infected with different infection doses of oocysts (100,000 oocysts) in gnotobiotical piglets and 200,000 oocysts in conventional piglets). In infected gnotobiotical piglets, the APM activity was studied in the period from the 3rd to 11th day after infection (DAI) and in infected conventional piglets in the period of to the 2nd to 10th day after infection (DAI). Control piglets, in the group of the gnotobiotical animals at the age of 2 to 5 days in the group of the conventional animals at the age of 4 to 7 days, had different APM activity in the microvillous zone of the intestinal mucosa. It was stated that the microvillous zone of the intestinal mucosa gained higher values in control conventional piglets (+7.01 mean values of density). In infected gnotobiotical piglets the density fall of the reaction product of APM was demonstrated already on the third day with further marked reduction of APM density on the 4th day after infection in the whole small intestine with predominance of the persisting APM activity in ileum. Even despite the slight increase in the density of the reaction product of APM in the period from the 5th to 7th DAI (the highest increase in APM density on the 6th DAI), a further decrease of the activity was recorded again on the 8th and namely the 9th DAI in the whole small intestine (the lowest value of density was found in the rear jejunum), the ileum mucosa being affected, too. A slightly higher density of the reaction product of APM was found in the duodenum. On the 10th DAI the APM density started to change and on the 11th DAI in the duodenum and in the middle jejunum it even reached higher values in comparison with the control data. Some differences were proved in the infected conventional piglets in comparison with the development of the APM activity in the small intestine mucosa in the infected gnotobiotical piglets. On the 3rd and 4th DAI APM defect occurred in the whole small intestine, with APM density prevailing in the ileum mucosa (like in the group of infected gnotobiotical piglets). The second period of decrease in APM activity lasted for almost four days (6th to 9th DAI).(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of host maturity and prior exposure history on the production of Neospora caninum oocysts by dogs

To investigate whether dogs shed Neospora caninum oocysts more than once, five dogs with a previous history of shedding oocysts were fed infected bovine tissues. Two of three dogs shed oocysts when they were re-exposed 18-20 months after the first challenge; two other dogs re-exposed earlier, only 8 months after the primary exposure, did not produce oocysts. These results suggest that dogs may become refractory to shedding N. caninum oocysts for a period approximately between 8 and 18 months after a primary infection; however, this possibility requires statistical validation by testing of more dogs. The development of a high antibody titer did not ensure that a dog would completely resist shedding oocysts after consuming an infected meal. Oocyst production was also compared between puppies and adult dogs with primary infections. Twelve puppies (three from the present study and nine from a previous study) shed significantly more oocysts (mean: 166,400) compared with five adult dogs following primary exposure (mean: 2900), indicating that a dog's age can influence N. caninum oocyst production (P=0.02).     

Group A rotavirus excretion patterns in naturally infected pigs

Cross-sectional and cohort studies were conducted in a piggery to investigate the excretion pattern of group A rotavirus in pigs. The cross-sectional survey revealed that 47 (9 per cent) of 521 pigs sampled were excreting rotavirus in the faeces. No rotavirus antigen was detected in the faeces of pigs either less than one week or over two months old. The prevalence of infection increased with age over the sucking period, and was greatest at five weeks old. Diarrhoea was observed in only eight (17 per cent) of the pigs excreting rotavirus. Sixteen piglets from four litters were selected and faecal samples collected daily from each animal from birth to two months old. All the piglets excreted group A rotavirus and the range of ages at which they first became infected was between 13 and 39 days. The average duration of excretion in individual piglets was 7.4 days. Ten of 13 sucking piglets which excreted rotavirus developed diarrhoea soon after it was first detected.     

Effects of intermittent and continuous administration of decoquinate on bovine coccidiosis in male calves

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.     

The effect of Eimeria acervulina infection on hearts of young broiler chicks

Hearts from 2-to-3-week-old broiler chicks that were inoculated with 2 X 10(6) sporulated oocysts/bird weighed significantly less than hearts from control chicks at 4 and 7 days postinoculation (PI). However, heart weights of infected chicks expressed as percentage of body weights were not significantly different from those of controls throughout the experiment. Infection also had no significant effect on heart protein content. Cardiac glycogen was significantly increased at 7 days PI but not at 4 days PI. Oxidation of both alpha-ketoglutaric and octanoic acids by mitochondrial preparations from hearts of infected chicks was significantly depressed at 4 days PI compared with controls; at 7 days PI, however, oxidation of octanoic acid was significantly increased, but that of alpha-ketoglutaric acid was not.     

Experimental Eimeria bovis infection in calves: a histopathological study.

Eight male holstein calves, four to six weeks of age, were infected with 100,000 sporulated oocysts of a culture containing Eimeria bovis. The calves were injected with steroids on days 13, 14 and 15 and killed on days 16, 18, 19, 20, 21, 22, 24 and 26 postinfection. The lesions caused by experimental E. bovis infection in the small and large intestines are characterized by a diphtheritic typhilitis and colitis. Severe lesions were also seen in the last metre of the ileum in a calf killed 19 days after infection. Most of the damage of the intestinal mucosa is caused by the sexual stages. There is destruction and loss of epithelial cells with subsequent exposure of lamina propria and formation of diphtheritic membranes.     

Pathogenicity of experimental infection with 'pneumotropic' porcine coronavirus

Virus localisation and lesions were studied in 14-one-week-old piglets following combined intranasal-oral inoculation with a British isolate of 'pneumotropic' porcine coronavirus (PCV) and were compared with the effects of transmissible gastroenteritis virus (TGEV) infection in five piglets. Unlike TGEV-infected piglets, all PCV-inoculated piglets remained clinically healthy. Seroconversion was detected at seven days after inoculation. Mild bronchointerstitial pneumonia involving terminal airways was consistently present at two days after infection and thereafter. Both PCV and TGEV infected bronchiolar epithelium and alveolar macrophages but, unlike TGEV, replication by PCV in villous enterocytes was limited and did not cause villous atrophy.     

Role of acquired immunity and natural age resistance on course of Isospora suis coccidiosis in nursing piglets.

Thirty-two piglets from three litters were experimentally inoculated with 200000 sporulated oocysts of Isospora suis at 3 days of age and/or rechallenged at 19 days of age or primary inoculated at 19 days of age, to compare the role of acquired immunity and natural age resistance on the course of coccidiosis. Twelve piglets were not inoculated and served as a control. Following challenge, the signs of coccidiosis characterised by clinical symptoms, oocysts shedding and weekly weights were similar to those which occurred in piglets primary inoculated at 19 days of age. This comparison suggests that maturation of non-specific components of the immune system plays a more important role in the resistance of neonatal piglets to I. suis infection than specific immune mechanisms.