Porcine neonatal coccidiosis in quebec

Intestinal coccidiosis was diagnosed in 110 diarrheic piglets originating from 66 farrowing operations. These piglets had been submitted alive for necropsy early after the beginning of diarrhea, and the diagnosis of coccidiosis was based on the demonstration of coccidial forms in their jejunum by histopathological examination. Enteropathogenic strains of Escherichia coli were demonstrated in only nine of the 110 piglets while the transmissible gastroenteritis virus and rotavirus were each present in three pigs. The most common lesion was a multifocal villous atrophy in the middle and lower jejunum, and ileum of the affected pigs. Coccidial forms were present in variable numbers of the cells lining the affected villi and they were mainly asexual stages (meronts and merozoites).

In the affected farrowing houses diarrhea began between five and 15 days of age with the highest frequency around seven to ten days of age. Morbidity rates were very variable and mortality was less than 20%. The disease was a persistent problem in large farrowing operations on continuous farrowing programs, and losses were due mainly to retarded growth and treatment costs which were usually inefficient. The disease occurred year round with the highest prevalence in summer and fall months, and in January.

Search for oocysts in fecal samples or colonic contents from 28 of the 110 pigs revealed that 13 of them were shedding oocysts identified as Isospora suis.

     

Several enteropathogens are circulating in suckling and newly weaned piglets suffering from diarrhea in the province of Villa Clara, Cuba

Intestinal contents of suckling (n?=?45) and newly weaned (n?=?45) piglets, suffering from diarrhea in the province of Villa Clara in Cuba, were tested for viral, bacterial, and parasitic enteropathogens from May to June 2008. At least one enteropathogen was identified in 53.3 % of piglets and enterotoxigenic Escherichia coli (ETEC; 25.6 %) was the major pathogen; mostly STa⁺/STb⁺ or F4⁺/STa⁺/STb⁺ ETEC were isolated. The overall occurrence of the rest of pathogens was 10 % for transmissible gastroenteritis virus (TGEV) and Cryptosporidium parvum, 6.7 % for rotavirus A and Isospora suis, 5.6 % for α-toxigenic Clostridium perfringens, 3.3 % for verotoxigenic E. coli (VTEC), and 2.2 % for Salmonella enterica subspecies enterica serovar Newport. TGEV and α-toxigenic C. perfringens were only identified in suckling piglets, while Salmonella Newport and VTEC were only detected in weaned pigs. Porcine epidemic diarrhea virus (PEDV), β-toxigenic C. perfringens, Eimeria spp., and helminths were not identified. Eight kinds of mixed infections were detected in 25 % of enteropathogen positive piglets. ETEC was present in 10 of 12 mixed infections, and TGEV infections were never combined. This survey demonstrates that several enteropathogens are circulating in piggeries located in the province of Villa Clara in Cuba, and that is necessary to improve surveillance, prevention, and control of enteric infections in order to increase production efficiency.     

Identification of atypical rotaviruses in outbreaks of preweaning and postweaning diarrhea in Québec swine herds.

Intestinal contents of diarrheic pigs from 120 outbreaks of diarrhea were examined for the presence of atypical rotaviruses. Pigs involved in these outbreaks were aged two days to five weeks and samples collected over a period of one year originated from different regions of the province of Québec. Samples were analyzed by polyacrylamide gel electrophoresis (PAGE) for the presence of viral RNA and genome profiles were compared to those of porcine rotavirus A/OSU, B/Ohio and C/Cowden. Based on electropherotypes both typical (group A) and atypical (groups B and C) rotaviruses were identified. Rotaviruses could be demonstrated in 25.8% of outbreaks and together atypical rotaviruses accounted for 46.7% of rotavirus-positive outbreaks. Other common enteropathogens were often present in conjunction with rotaviruses in the preweaning and postweaning outbreaks studied.     

Risk factors of weaning diarrhea in puppies housed in breeding kennels

Diarrhea represents one of the most frequent disorders in dogs. In puppies, degradation of feces quality is associated with a reduced daily weight gain and an increased risk of death. Prevention of diarrhea in puppies requires a global approach encompassing enteropathogens, environment and management practices especially when housed in groups. The purpose of this study was to determine prevalence of enteropathogens in puppies in breeding kennels and to identify risk factors of diarrhea. Two hundred and sixty six puppies (between 5 and 14 weeks of age) from 29 French breeding kennels were included. For each kennel, data about environment, management of the kennel and puppies’ characteristics (age, sex and breed) were collected. For each puppy, fecal consistency and fecal excretion of enteropathogens (viruses and parasites) was evaluated. At least one enteropathogen was identified in 77.1% of puppies and 24.8% of puppies presented abnormal feces. The main risk factor of weaning diarrhea was fecal excretion of canine parvovirus type 2 (odds ratio = 5; confidence interval 95%: 1.7–14.7). A targeted sanitary and medical prophylaxis against canine parvovirus type 2 should be implemented to decrease risk of weaning diarrhea.     

An investigation into the association between cpb2-encoding Clostridium perfringens type A and diarrhea in neonatal piglets

To investigate the possible role of cpb2-positive type A Clostridium perfringens in neonatal diarrheal illness in pigs, the jejunum and colon of matched normal and diarrheic piglets from 10 farms with a history of neonatal diarrhea were examined grossly and by histopathology, and tested for C. perfringens, for C. perfringens beta2 (CPB2) toxin, as well as for Clostridium difficile toxins, Salmonella, enterotoxigenic Escherichia coli, rotavirus, transmissible gastroenteritis (TGE) virus, and coccidia. Clostridium perfringens isolates were tested using a multiplex real-time polymerase chain reaction (PCR) to determine the presence of cpa, consensus and atypical cpb2, and other virulence-associated genes. The numbers of C. perfringens in the intestinal contents were lower in diarrheic piglets (log₁₀ 5.4 CFU/g) compared with normal piglets (log₁₀ 6.5 CFU/g) (P < 0.05). The consensus cpb2 was present in 93% of isolates in each group, but atypical cpb2 was less common (56% healthy, 32% diarrheic piglets isolates, respectively, P < 0.05). The presence of CPB2 toxin in the intestinal contents of normal and diarrheic piglets did not differ significantly. Clostridium difficile toxins and rotavirus were each detected in 7 of the 21 (33%) diarrheic piglets. Rotavirus, C. difficile toxins, Salmonella, or enterotoxigenic E. coli were concurrently recovered in different combinations in 4 diarrheic piglets. The cause of diarrhea in 8 of the 21 (38%) piglets on 6 farms remained unknown. The etiological diagnosis of diarrhea could not be determined in any of the piglets on 2 of the farms. This study demonstrated that the number of cpb2-positive type A C. perfringens in the intestinal contents was not a useful approach for making a diagnosis of type A C. perfringens enteritis in piglets. Further work is required to confirm whether cpb2-carrying type A C. perfringens have a pathogenic role in enteric infection in neonatal swine.     

High prevalence of F4<Superscript>+</Superscript> and F18<Superscript>+</Superscript><Emphasis Type="Italic">Escherichia coli</Emphasis> in Cuban piggeries as determined by serological survey

Little information is available on the prevalence of swine enteropathogens in Cuba where diarrheic diseases are responsible for 31% and 37% of the total mortality during the neonatal and postweaning periods. F4⁺ and F18⁺ enterotoxigenic Escherichia coli and F18⁺ verotoxigenic E. coli induce diarrhea and edematous disease in pigs, but their distribution has never been thoroughly studied in the Cuban swine population. Therefore, the present study estimated the prevalence of F4- and F18-specific antibodies in sera of 1,044 6-month-old gilts distributed in 34 piggeries spread over the Cuban territory. For the data analysis, which included the optical density of individual samples tested by ELISA, random-effects models and a mixture model in R (package “mixAK”; Komárek, Computational Statistics and Data Analysis 53:3932–3947, 2009) were fitted. Low, moderate, and high levels of F4-specific antibodies were found in 67.6%, 26.8%, and 5.6% of the gilts, while 66.4% and 33.6% of gilts showed low and high levels of F18-specific antibodies. Hereby, we show that F4⁺ and F18⁺ E. coli are highly prevalent as potential enteropathogens in Cuban piggeries.     

Rotavirus and concurrent infections with other enteropathogens in neonatal diarrheic dairy calves in Spain

Faeces samples from 218, one to 30 days old, diarrheic dairy calves in 65 dairy herds were screened for the presence of rotavirus and concurrent infections with coronavirus, Cryptosporidium, F5+ Escherichia coli and Salmonella spp. Calves were grouped according to their age as follows: 1-7, 8-14, 15-21 and 22-30 days. Rotavirus infection was detected in 46.9%, 45.6%, 33.8% and 48.3% of the calves in the respective age-groups. No significant differences in the detection rate of rotavirus were found among calves on the different age-groups. Rotavirus was the only enteropathogen detected in 39 of the 93 (41.9%) diarrheic calves positive to this agent. Concurrent infections with other enteropathogen(s) were detected in 31.3%, 33.3%, 20.6% and 3.4% of the rotavirus infected calves in the age-groups 1-7, 8-14, 15-21 and 22-30 d, respectively. A significant age-associated decrease in the detection rate of mixed infections (p < 0.01) was found. The detection rates of the other enteropathogens considered in calves with rotavirus infection were 20.4% for coronavirus, 85.2% for Cryptosporidium, 16.7% for F5+ E. coli and 1.8% for Salmonella.     

Oral transmission of transmissible gastroenteritis virus by muscle and lymph node from slaughtered pigs

A study was conducted in the USA to determine whether transmissible gastroenteritis (TGE) virus could be transmitted from carcases of slaughtered pigs. Transmissible gastroenteritis virus was transmitted to 6-day-old piglets by dosing with homogenates of muscle and lymph node collected from 500 clinically normal pigs at the time of slaughter. All piglets in 2 separately housed litters showed clinical signs of TGE with 5 piglets dying within 10 d of oral dosing with homogenates. Transmissible gastroenteritis virus was isolated from 2 of these piglets and all piglets developed TGE antibody. Transmissible gastroenteritis virus was not isolated in tissue culture from muscle and lymph node homogenates, but was isolated from 4 (0.8%) of 500 tonsil samples collected from the same pigs. A survey of 250 serum samples provided an estimate of the prevalence of slaughtered pigs with TGE antibody of 34.8% in the sample population. The results indicate that carcases of some pigs from TGE endemic areas contain viable TGE virus, and that there would be a substantial risk of introducing TGE virus into Australia by the importation of uncooked pig meat from these areas.     

An epidemiological survey on pigs showing symptoms of infectious enteric diseases and dyspepsia in Japan

Diarrhea in pigs has the potential to have a serious economic impact on the swine industry. Previously, we suggested that the likely cause of the presence of non-infectious diarrhea in pigs characterized by lactate accumulation was dyspepsia. In this experiment, the prevalence of enteropathogens and hyper-lactate accumulation in feces of piglets in 4 distinct growth stages was examined. The feces were collected when veterinarian experts recognized abnormalities in sporadic outbreaks. Prevalence of enteropathogens in diarrheal feces was 100% in fattening pigs (FP), 75% in weaning pigs (WP), 50% in suckling pigs (SP), and 42% in growing pigs (GP). Prevalence of enteropathogens in loose feces was 53% in WP, 50% in SP, 40% in FP, and 28% in GP. Prevalence of hyper-lactate accumulation in diarrheal feces was 33% in GP, 33% in SP, 25% in WP, and 25% in FP. Prevalence of hyper-lactate accumulation in loose feces was 40% in GP, 0% in SP, 7% in WP, and 5% in FP. Accordingly, non-infectious dyspepsia is frequent in growing pigs. In this period, pigs are potentially exposed to needless antimicrobial therapeutic treatments in sporadic cases.     

Prevalence of Cryptosporidium parvum infection in Punjab (India) and its association with diarrhea in neonatal dairy calves

A prevalence study was contemplated to determine the prevalence of Cryptosporidium spp. in dairy farms in Punjab, India. The cryptosporidium oocysts were detected from 50 and 25.68% from 80 diarrheic and 74 non-diarrheic animals, respectively. Both shedding and intensity of shedding were significant in calves with diarrhea. The Cryptosporidium spp. appears to be common in dairy calves and an important contributor of calf diarrhea in the Punjab province. The prevalence of the infection peaked in young calves between 0 and 30 days in both the diarrheic and non-diarrheic groups (86.4 and 66.6%, respectively). The percentage distribution of positive samples, with reference to age groups of diarrheic and non-diarrheic animals was negatively correlated with increase in age. High mortality rate and case fatality rate of 35.2 and 44.4% were observed in young calves between 0 and 30 days of age.     

Prevalence,prediction and risk factors of enteropathogens in normal and non-normal faeces of young Dutch dairy calves

Between January and April 2007, 424 calves under 22 days of age from 108 Dutch dairy herds were sampled to estimate the prevalence of non-normal faeces (‘custard-like’—yellowish-coloured with custard consistency or diarrhoea: watery-like faeces) and the shedding of enteropathogens Escherichia coli K99 (E. coli), Coronavirus, Cryptosporidium parvum (C. parvum), Rotavirus and Clostridium perfringens (Cl. perfringens). In addition, information was collected on animal characteristics and herd-management practices. The probability of detecting each one of five enteropathogens given a calf with ‘custard-like’ faeces or diarrhoea was estimated using Bayes’ rule and was based on the predicted probabilities from a multinominal model including each of five enteropathogens as independent variables. In addition, putative risk factors for the presence of each of five enteropathogens were analysed using logistic regression models with random herd effects.Fifty-seven percent of calves had faeces of normal colour (brownish) and consistency (firm), 23.8% (95%CI: 19.8–28.2%) had ‘custard-like’ faeces and 19.1% (95%CI: 15.5–23.2%) had diarrhoea. E. coli was the least detected enteropathogen (2.6% (95%CI: 1.3–4.6%) of calves, 9% (95%CI: 5–16%) of herds) and Cl. perfringens was most detected (54.0% (95%CI: 49.1–58.8%) of calves, 85% (95%CI: 77–91%) of herds). E. coli and Coronavirus were detected incidentally in only one or two calves per herd, whereas C. parvum and Cl. perfringens were frequently detected in up to four calves per herd. For calves with ‘custard-like’ faeces, the probability of detecting Rotavirus from a calf in its first week of age was 0.31 whereas for a calf in its second week, there was a 0.66 probability of detecting C. parvum. The probabilities of detecting E. coli, Rotavirus and C. parvum in calves with diarrhoea in their first week of age were 0.10, 0.20 and 0.43, respectively. In calves with diarrhoea between 1 and 2 weeks of age, the probability of detecting enteropathogens was 0.43 for C. parvum. None of the tested enteropathogens were related to ‘custard-like’ faeces or diarrhoea in the third week of age.Putative risk factors for E. coli, Coronavirus and C. parvum included the presence of peer-calves shedding Coronavirus, C. parvum or Rotavirus, respectively. Additionally, managerial risk factors such as non-optimal hygienic housing (for Coronavirus) and the routine use of antibiotics for diarrhoeic calves (for C. parvum) were found. No animal or managerial factors were associated with shedding of Cl. perfringens.     

Isolation and association of Escherichia coli AIDA-I/STb, rather than EAST1 pathotype, with diarrhea in piglets and antibiotic sensitivity of isolates.

To identify emerging Escherichia coli that have the potential to cause diarrhea in pigs, the prevalence of E. coli pathotypes was determined among 170 and 120 isolates from diarrheic and nondiarrheic piglets, respectively. The isolates were tested for F4, F5, F6, F18, and F41 fimbriae, for E. coli attaching and effacing (EAE), porcine attaching and effacing-associated (Paa), and adhesin involved in diffuse adherence (AIDA-I) factors, for LT, STa, STb, and enteroaggregative heat-stable (EAST1) enterotoxins, and for Shiga toxins (Stxl, Stx2, and Stx2e), using DNA hybridization and polymerase chain reaction. All isolates were O-serotyped and tested for antibiotic resistance against 10 drugs. Seventeen different pathotypes, accounting for 40.0% of the isolates, were recovered from diarrheic piglets. The main pathotypes included EAST1 (13.5%), F4/LT/STb/EAST1 (6.5%), AIDA-I/STb/EAST1 (4.1%), F5/STa (2.9%), EAE/EAST1 (2.9%), and AIDA-I/F18 (2.3%). Only 3 pathotypes, EAE (11.7%), EAST1 (10.8%), and EAE/EAST1 (3.3%), were recovered from nondiarrheic piglets. Paa factor was detected in 8.8% and 7.5% of isolates from diarrheic and nondiarrheic piglets, respectively, and always was associated with other virulence determinants. Overall, 22.9% of isolates from diarrheic piglets appeared to be enteropathogens: enterotoxigenic E. coli (11.7%), enteropathogenic E. coli (3.5%), and E. coli isolates (3.0%) for which none of the above adherence factors was detected. Pathotypes AIDA-I/STb/EAST1 and AIDA-I/STb were isolated only from diarrheic piglets and accounted for 4.7% of isolates. Strains of these pathotypes induced diarrhea when inoculated into newborn colostrum-deprived pigs, in contrast to an isolate positive only for EAST1, which did not induce diarrhea. Antibiotic sensitivity test showed that isolates of the AIDA-I/STb/EAST1 and AIDA-I/STb pathotypes were the only strains sensitive to enrofloxacin, gentamicin, neomycin, and trimethoprim-sulfamethoxazole. This study showed that at least 20.5% of isolates from diarrheic piglets appeared to be associated with AIDA-I/STb pathotype and that EAST1 pathotype is probably not an important marker for diarrhea in piglets.     

Prevalence and risk factors associated with Cryptosporidium oocysts shedding in pigs in Central Vietnam

We investigated the prevalence and risk factors associated with Cryptosporidium oocysts shedding in pigs in Central Vietnam. A total of 740 single fecal samples collected from diarrheic and non-diarrheic pigs on 89 farms were screened by the modified Ziehl-Neelsen staining method. Prevalence at the animal and the farm levels were 18.1% (134/740) and 71.9% (64/89), respectively. Risk factors for the infection were identified using univariate and multivariate logistic regression analysis. The results revealed that age, sanitary condition and topography were significantly associated with oocyst shedding (P<0.05). Pre-weaned piglets were at the highest risk for infection, followed by post-weaners, sows and finishing pigs. Good sanitary conditions showed positive effects in decreasing oocysts shedding. Topographically, Cryptosporidium was more common in mountainous zone than that in coastal delta zone. There was an association between the occurrence of diarrhea and the level of Cryptosporidium oocyst excretion within infected pigs. This is the first epidemiological investigation of prevalence and risk factors of Cryptosporidium in pigs in Vietnam.     

Rotavirus as a cause of diarrhea in pigs.

A rotavirus (reovirus-like agent) was associated with diarrheal diseases occurring in 1- to 4-week-old suckling pigs in 8 herds and in weaned pigs in 2 herds. Transmissible gastroenteritis virus was also detected in 2 of these herds, as was enteropathogenic Escherichia coli in 5 herds. Morbidity was generally greater than 80% in pigs of the affected age group within these herds, and mortality from diarrhea ranged from 7 to 20%. The disease due to rotavirus in suckling pigs appeared similar to the syndrome commonly referred to as milk scours, white scours, or 3-week scours. Diarrhea and villous atrophy, resembling that seen in transmissible gastroenteritis, occurred in naturally infected pigs and in gnotobiotic pigs experimentally infected with rotavirus. Diagnosis was accomplished by immune electron microscopy of intestinal contents and by immunofluorescent staining of enterocytes. A massive infection of enterocytes with rotavirus was demonstrated by immunofluorescence, which helps explain the pathogenesis of this disease. The apparent rarity of clinical rotaviral infections in suckling pigs greater than 7 days old is probably due to the acquisition of passive immunity from immune sows.     

Genotypes and antibiotic resistance of canine Campylobacter jejuni isolates

Campylobacter jejuni is the most important cause of bacterial gastroenteritis in humans. It is a commensal in many wild and domestic animals, including dogs. Whereas genotypes of human and chicken C. jejuni isolates have been described in some detail, only little information on canine C. jejuni genotypes is available. To gain more information on genotypes of canine C. jejuni and their zoonotic potential, isolates from routine diagnostics of diarrheic dogs as well as isolates of a prevalence study in non-diarrheic dogs were analyzed. Prevalence of thermophilic Campylobacter among non-diarrheic dogs was 6.3% for C. jejuni, 5.9% for Campylobacter upsaliensis and 0.7% for Campylobacter coli. The C. jejuni isolates were genotyped by multi locus sequence typing (MLST) and flaB typing. Resistance to macrolides and quinolones was genetically determined in parallel. Within the 134 genotyped C. jejuni isolates 57 different sequence types (ST) were found. Five STs were previously unrecognized. The most common STs were ST-48 (11.2%), ST-45 (10.5%) and ST-21 (6.0%). Whereas no macrolide resistance was found, 28 isolates (20.9%) were resistant to quinolones. ST-45 was significantly more prevalent in diarrheic than in non-diarrheic dogs. Within the common time frame of isolation 94% of the canine isolates had a ST that was also found in human clinical isolates. In conclusion, prevalence of C. jejuni in Swiss dogs is low but there is a large genetic overlap between dog and human isolates. Given the close contact between human and dogs, the latter should not be ignored as a potential source of human campylobacteriosis.     

Studies on preweaning piglet diarrhoea

SUMMARY The aim of this study was to determine the cause and risk factors Involved in preweaning piglet diarrhoea. Faecal samples from 2380 diarrhoeic piglets, 5 to 30 days of age, were examined for enteropathogens. Isospora suls oocysts were detected in 53.8% of samples, Escherichia coll in 18.2% and rotavirus in 16.9%. I suis had the widest distribution, being present on 70.9% of 151 piggeries. The onset of diarrhoea occurred mainly between 7 and 14 days (77.5%), peaking at 10 days. Records of 4086 litters from two intensive piggeries were analysed and showed no seasonal variation or effect of sow parity on the incidence of piglet diarrhoea. I suis was the most common enteropathogen associated with diarrhoea in piglets from 5 days of age until weaning.     

The Significance of Proliferation and Enterotoxin Production by Escherichia coli in the Intestine of Gnotobiotic Pigs

The significance of enterotoxin production and proliferative ability of Escherichia coli in the intestinal tract as related to porcine enteric colibacillosis was studied in 68 gnotobiotic pigs.

The animals were monocontaminated at seven to ten days of age with eight selected strains of E. coli. The strains were two naturally occurring porcine enteropathogens — P155 (0149:K91;K88a,c:H10) and P307 (08:K87;K88a,b:H19), two nonenteropathogenic strains — P104 (0139:K82:H1) and F11 (018-ab:K?:H14), and four enterotoxigenic derivatives of the above strains — P104(P155), P104(P307), F11(P155) and F11(P307). The response of the animals was evaluated on the basis of clinical observations and necropsy lesions 22 hours after exposure to the organisms. E.coli counts were determined at seven different levels of the intestinal tract. Cell free extracts of the intestinal contents were examined for enterotoxic activity by the ligated pig intestine loop test.

All of the strains possessing the enterotoxin plasmid produced enterotoxin in the pig's intestine and were capable of causing diarrhea. The nonenteropathogenic E. coli failed to do so. The strains possessing the P155 enterotoxin plasmid were more virulent than the corresponding derivatives with the P307 enterotoxin plasmid. Strains P155, P307 and P104(P155) proliferated in the upper small intestine at a greater rate and were more virulent than the other strains. The numbers attained in the upper small intestine by the other enterotoxigenic derivatives were comparable to those of their nonenteropathogenic parent strains.

It was considered that enterotoxin produced by E. coli was the essential factor for causing a diarrheic response in gnotobiotic pigs. The virulence of each of the tested strains appeared to be governed by the degree of enterotoxicity associated with a particular enterotoxin plasmid, the numbers attained by these organisms in the upper small intestine, (but not in the lower small intestine or in the colon), and by other undetermined factors.

     

Bovine Cryptosporidiosis: Clinical and Pathological Findings in Forty-two Scouring Neonatal Calves

Cryptosporidia organisms were identified in 42 of 161 (26%) neonatal, diarrheic calves, over a 32 month period commencing July 1979. Forty of the 161 calves were submitted alive and cryptosporidiosis was diagnosed in 63% (25 of 40) of them. The cryptosporidia infected calves were usually one to two weeks old and came from 26 herds where the typical history was profuse, watery diarrhea in nearly all neonatal calves. The diarrhea usually started around one week of age, was unresponsive to all conventional antidiarrhea therapies, lasted for two or more weeks and was usually fatal. Twenty-nine (69%) of the cryptosporidia infected calves were submitted between December and February. These calves were often hutch reared.

Histopatholoical examination revealed large numbers of the coccidial parasite Cryptosporidium sp embedded in the microvilli of jejunal and ileal absorptive enterocytes of all affected calves. The organisms were identified as trophozoites and schizonts (asexual stages) and macrogametes (female sexual stages) with the electron microscope. Microgametes (male sexual stages) were not identified. Occasionally a merozoite (asexual stage) was also seen apparently burrowing into or about to be enveloped by a host microvillus. Observation of the organisms was much easier when diarrheic calves were submitted alive. Enterotoxigenic Escherichia coli were often cultured from intestines of dead calves and occasionally from calves submitted alive. Coronavirus particles were seen in one calf. In the last year of this study, oocysts were identified in fecal smears stained with May-Grünwald-Giemsa stain and fecal samples using a dichromate solution flotation technique.

     

Production of porcine aminopeptidase N (pAPN) site‐specific edited pigs

Porcine viral diarrhea is an acute and highly contagious enteric disease in pigs which causes huge economic losses in pig industry worldwide. Transmissible gastroenteritis virus (TGEV) is main pathogens responsible for piglets viral diarrhea. Knockout the host cellular surface receptor for TGEV may be an effective way to accelerate the breeding of resistant pigs. In this study, we applied site‐specific editing pAPN which is effective in swine testis (ST) cells. Site‐specific editing of pAPN reduced TGEV proliferation in ST cells by 96%–99% at different time periods post‐infection. Next, the site‐specific editing of pAPN porcine fetal fibroblasts were produced, and then the cell colonies were used as donor cells to generate the site‐specific editing of pAPN pigs. Our research findings will not only offer a more thorough understanding of the pathogenesis of piglet diarrhea and lay the foundation for breeding TGEV‐resistant piglets, but also understanding the molecular mechanisms involved in coronaviral infections.