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.     

Transfer of maternal antibody against group A rotavirus from sows to piglets and serological responses following natural infection

An enzyme-linked immunosorbent assay (ELISA) was developed for the measurement of antirotaviral antibody in sera and faeces from pigs and used to study the dynamics of antirotaviral antibody responses in three cohorts of pigs. Piglets acquired antirotaviral antibody by sucking their dams soon after birth. Antirotaviral antibodies of IgA and IgG classes were detected in both colostrum and milk of all sows tested but IgM class antibodies were not. The antibody levels in colostrum were eight to 32 times higher than those in milk which was collected 18 days post partum. The levels of antibody in piglets' sera were comparable to those in colostrum but declined quickly to low levels by one month old. Maternal antibody was also detected in the faeces of piglets up to 18 days old. Natural rotavirus infection occurred in each of these cohorts when the geometric mean ELISA titres of maternal antibody in their sera declined to 1/1600 (by days 21, 25 and 30 for cohorts 1, 2 and 3, respectively). However, a positive correlation was not obtained between the levels of antirotaviral antibody and protection in individual litters within each of the cohort groups. In each of the cohorts, rotavirus infection usually occurred in one or two piglets first and then spread to other piglets in the same cohort. It is therefore suggested that maternally derived antibody is protective against rotavirus infection in piglets only for the first one or two weeks. Following natural infection with rotavirus, increases in serum antibodies were detected in two of the three cohorts by 20 to 30 days after the average time of onset of faecal shedding of virus.(ABSTRACT TRUNCATED AT 250 WORDS)     

断奶日龄对仔猪断奶期腹泻和死亡影响的研究

选择杜洛克×豫农白猪Ⅰ系杂交仔猪８窝共７２头，均分为两组，每组４窝３６头。试Ⅰ组采用２８日龄断奶，试Ⅱ组采用３５日龄断奶。试验期从断奶前１周至６０日龄，分析比较不同断奶日龄对仔猪断奶期腹泻和死亡的影响。结果：①试Ⅰ组和试Ⅱ组仔猪，断奶后至６０日龄间发生腹泻１５９头次和８５头次，全群日平均腹泻发生率为１４．７６％和９．０８％；②试Ⅰ组和试Ⅱ组仔猪，断奶后至６０日龄间死亡数为４头和０头；③试Ⅰ组和试Ⅱ组仔猪，断奶后至６０日龄发生腹泻的高峰期在断奶后５～２２天和断奶后３～８天，持续期为１８天和６天，日腹泻发生率最高达４２．４２％和３３．３３％；④试Ⅰ组４窝仔猪在断奶至６０日龄期间，有３窝出现多个腹泻高峰，只有１窝为１个高峰；而试Ⅱ组４窝仔猪中，只有１窝出现多个腹泻高峰，其它３窝为１个高峰。     

Rotavirus associated diarrhoea in nursing piglets and detection of antibody against rotavirus in colostrum, milk and serum

A blocking method of ELISA for the detection and quantification of antibody against porcine rotavirus in serum, colostrum and milk has been compared with a plaque reduction test. The results obtained with the two techniques correlated (Fig. 1). Antibody against rotavirus was demonstrated in 384 serum samples representing 25 swine farms, indicating a widely spread and dense distribution of the infection with porcine rotavirus among Danish swine. The antibody contents in milk samples from 7 gilts and sows from 2 farms with a previously diagnosed problem with rotavirus associated diarrhoe showed a rapid decline during the first few days of the lactation periods (Fig. 1). An increase in the contents of rotavirus specific antibody was observed from day 15 in the milk samples from one of the gilts. The excretion of rotavirus with feces from the 7 litters of piglets were followed through the suckling period. Rotavirus war found in all litters but one and the virus was excreted in periods ranging from 4 to 9 days.     

Studies of transplacental and perinatal infection with two clones of a single Aujeszky's disease (pseudorabies) virus isolate

The effect of Aujeszky's disease virus (ADV) infection in the last third of gestation was studied using two clones from an ADV isolate. Twelve sows were infected with one or other clone at 85 +/- 1 days of gestation. The dose of infection was 5 X 10(6) TCID50 per sow. The clinical and serological responses to the infection were different. One clone, Ls-1, produces a severe and acute illness. The course of the disease went from 9 to 14 days while the other clone, Ls-2, caused a mild or silent infection and for a shorter time. Transplacental infection occurred in only one sow which had been infected with Ls-2. The litter consisted of 8 mummified fetuses. Sows infected with Ls-1 produced piglets or mummified fetuses that were virus-negative. Perinatal infection was found in litters from both groups. Colostrum-deprived piglets that did not have postpartum contact with the sow, produced specific antibodies, 2 out of 6 born to sows infected with Ls-1 and 1 out of 4 born to sows infected with Ls-2. The antibody titers in colostrum-fed piglets were related to the extent of clinical response of the sows to the infection. Litters born to sows infected with Ls-1 had mean SNT titers from 1/12 to 1/112 while litters born to sows infected with Ls-2 showed titers of 1/2 or less than 2.     

Experimental infection of piglets by aerosols of Rhodococcus equi.

The purpose of this study was to investigate experimental infection of the piglet as a model of Rhodococcus equi pneumonia in the foal. Three litters of eight piglets each were exposed to an aerosol of 3.4 X 10(7) R. equi per piglet per day for seven consecutive days. Over the next 23 days the piglets were observed for clinical signs of disease. Periodically after infection one piglet from each litter was killed, the lungs were cultured quantitatively for R. equi and the gross and microscopic pulmonary lesions were assessed. The only clinical evidence of disease was the occurrence of elevated temperatures in the infected piglets. Rhodococcus equi was slowly cleared from the piglets' lungs during the 23 days following aerosolization. Piglets sacrificed seven to ten days after aerosolization had the most extensive pulmonary lesions, consisting of severe consolidation of the cranioventral lobes. Microscopic examination revealed thickened interalveolar septa and alveoli containing many neutrophils and macrophages with intracytoplasmic Gram-positive coccobacilli. The pulmonary lesions in these piglets differed from those of naturally infected foals in that they were not characterized by macrophage-rich abscesses and the infection gradually resolved.     

Experimental production of congenital persistent swine fever infections: I. Clinical,pathological and virological observations

Twelve sows were inoculated with a low-virulent field strain of swine fever (SF) virus at 40, 65 and 90 days of pregnancy. Transplacental infection occurred in eight sows and these farrowed 88 piglets.Prenatal mortality was highest in litters from sows infected at 40 days after service, and postnatal death was most frequent in litters from sows infected at 65 days. Three sows gave birth to completely infected litters, whereas the five others farrowed litters in which uninfected piglets were found. The later the sows were infected during pregnancy, the more uninfected piglets were born. Twelve piglets recovered from the infection and the percentage of recoveries increased with the stage of pregnancy at which inoculation took place. Twenty-three piglets developed a persistent infection. The earlier infection occurred during pregnancy, the more persistent infections were produced. The persistently infected pigs developed a runting syndrome from about one week after weaning. The clinical signs were more severe in pigs from sows infected at 65 days of pregnancy than in pigs from sows infected at 40 days. A persistent viraemia was present in these pigs with titres ranging between 10^5.7 and 10^7.0 plaque forming units/ml of plasma. At autopsy the most pronounced lesions were an atrophy of the thymus, and swollen and pale lymph nodes. Virus antigen was present in lymphoidal, reticulo-endothelial and epithelial tissues.One persistently infected pig survived superinfection with a virulent strain of SF virus for 45 days.     

Epidemiological studies of piglet diarrhoea in intensively managed Danish sow herds. III. Rotavirus infection

The prevalence of rotavirus infection was studied in 1090 litters from 26 sow herds. Samples of normal, semifluid and watery stools were examined for rotavirus by an ELISA-test on faeces. Rotavirus was detected in 77% of the herds and in 30.5% of the litters (prevalence rates). The highest prevalence rate was seen in piglets between 21 and 41 days of age. Gilts' litters had a very high prevalence during the first week of life. Apart from this, no difference was found between litters from gilts and older sows. Rotavirus was detected more frequently in semiliquid, loose stools than in normal or watery stools, and an association between virus detection and diarrhoea could not be demonstrated. However, litters which shedded rotavirus during the suckling period had lower weight gains and higher incidence rates of respiratory diseases than virus-free litters. Litters weaned at 2 weeks in battery cages had slightly increased risk of shedding rotavirus compared to litters weaned in more traditional systems. The study revealed that rotavirus is widespread in Danish swine herds. The findings give evidence to suggest that the type of mild diarrhoea in 3-week-old piglets known as steatorrhoea or "white scours" may be associated with rotavirus infection, possibly in combination with E. coli and other agents. The high prevalence in piglets weaned at 2 weeks plus the higher morbidity and mortality among such piglets sustain the conclusion that piglets should not be weaned before 3 weeks of age or below a body weight of 6-7 kg.     

Epidemiological studies of piglet diarrhoea in intensively managed Danish sow herds. IV. Pathogenicity of porcine rotavirus

Colostrum-deprived piglets inoculated with rotavirus 24 h after birth developed a profuse diarrhoea that spread to non-inoculated, colostrum-deprived litter mates and, occassionally, to colostrum-fed piglets. Case fatality rates in these 3 categories of piglets were 63.2%, 35.7% and 8.3%, respectively. Surviving piglets recovered in 1-2 weeks, but shedded virus via the faeces for up to 3 weeks p.i. The D-xylose test revealed severe malabsorption, with extremely flat absorption curves for up to 3-4 weeks p.i. Malabsorption was more marked in piglets with a long-lasting faecal virus excretion than in piglets where virus disappeared from the faeces within 10 days p.i. Infected piglets (colostrum-fed and colostrum-deprived) had decreased weight gains and were 5 days older at a bodyweight of 25 kg than non-inoculated controls. It is concluded that rotavirus is probably of significance in diarrhoeal syndromes in suckling piglets, alone or in combination with E. coli or other pathogens.     

Development of post-weaning diarrhoea in piglets. Relation to presence of Escherichia coli strains and rotavirus

Weaning of piglets complicated with an exposure to pathogenic strains of Escherichia coli was scrutinized in two sets. The first set comprised 20 animals representing two litters and the second set included 30 animals from five litters. The piglets were either left as controls or exposed to one or three pathogenic strains of E. coli. Aiming to simulate a natural exposure the challenge strains were spread on the floor of the pens at weaning. In addition the pigs experienced several non-infectious stress factors commonly occurring at that occasion. Some groups were given adrenocorticotropic hormone (ACTH), aiming to simulate a stressful weaning. The balance and the composition of the faecal coliform populations, measured by a metabolic fingerprinting method, was disturbed among all animals following weaning. This disturbance was more pronounced and lasted longer among piglets exposed to pathogenic strains of E. coli. All piglets exposed to pathogenic E. coli shed these strains in faeces. Diarrhoea was induced in the groups exposed to E. coli, but not among the control animals. Pigs not treated with ACTH and subjected to a single pathogenic strain of E. coli became infected but did not develop diarrhoea unless if coinciding with shed of rotavirus. Control pigs excreting rotavirus had no diarrhoea. Diarrhoea was most frequent in the groups exposed to three pathogenic strains of E. coli, and in these groups diarrhoea was seen in the absence of rotavirus. ACTH administration amplified the clinical signs. The litter of origin influenced the development of post-weaning diarrhoea.     

Porcine parvovirus- and porcine circovirus 2-associated reproductive failure and neonatal mortality in crossbred Indian pigs

The objective of this study was to detect the presence of porcine parvovirus (PPV) and porcine circovirus 2 (PCV2) in a farm showing reproductive failure and increased mortality in neonatal piglets by histopathological examination, polymerase chain reaction, and demonstration of viral antigen and nucleic acid. Out of 594 piglets farrowed by 70 first-parity gilts, nine (1.51%) mummified fetuses, 13 (2.19%) stillborn, and 572 (96.3%) live-born piglets were recorded. The average litter size at birth was 8.48 piglets per litter. One hundred ninety-four (33.91%) piglets died within 7 days of age. PPV was detected in five litters (7.14%) and two of them revealed coinfection with PCV2. The pathological lesions in the coinfected litters were more severe, indicating a synergistic action between the two viruses. Results of this study suggest for the first time occurrence of PPV and coinfection with PCV2 in crossbred Indian pigs affected with reproductive problem and neonatal mortality.     

Pathology of natural rotavirus infection in clinically normal calves

During a longitudinal study of the epidemiology of rotavirus infection in a calf rearing unit, excretion of virus in faeces was detected by enzyme-linked immunosorbent assay in 40 of 48 (83 per cent) unweaned calves aged between three days and five weeks. Fifty per cent of the infected calves had no clinical signs of disease. Enterocytes containing rotavirus antigen and intestinal lesions were found in all of 12 clinically normal calves selected for necropsy between days 1 and 4 of virus excretion. Stunting and fusion of villi, exfoliation, disarrangement and vacuolation of enterocytes and the presence of cuboidal enterocytes were observed in infected calves but not in rotavirus-free control calves. Lesions predominated in the upper small intestine, where rotavirus was most abundant, especially on the first two days of virus excretion. The numbers of enterocytes infected with rotavirus diminished before the lesions resolved.     

Effect of Supplementary Feeding Milk Replacer on Growth Performance,Nutrient Digestibility,Serum Biochemistry Indexes in Piglets during Lactation

This experiment was conducted to study the effect of supplementary feeding milk replacer on growth performance,nutrient digestibility,serum biochemistry indexes in piglets during lactation,and explore the feasibility of shorten the weaning age of piglets by feeding milk replacer. One hundred and twenty (twelve litters) 5 days old piglets with average body weight of (3.12±0.63)kg were assigned into two groups with sixty piglets per group (six litters)and one litter of piglets per replicate. The piglets in control group received supplementary creep feed and were weaned on 28 days old,whereas the piglets in experimental group received supplementary creep feed and milk replacer (creep feed:milk replacer=1:1) and were weaned on 21 days old. The piglets in experimental group were continued feeding with creep feed and milk replacer until 28 days old. All piglets were fed with same diets from 28 to 70 days old. The results showed as follows:① Comparing with control group,the body weight of piglets in experimental group were not significantly changed at 5,21,28 and 70 days old (P>0.05),ADFI and F/G were extremely significantly or significantly increased during 5 to 21 days old,22 to 28 days old and 5 to 28 days old (P < 0.01;P < 0.05),while ADG was extremely significantly decreased during 22 to 28 days old compared with control group (P<0.01).② The digestibility of GE,DM,OM and EE of experimental group were significant higher than control group (P<0.05).③ All serum biochemistry indexes between the two groups had no significant differences (P>0.05). In conclusion,supplementary milk replacer feeding could increase the feed intake and dietary digestibility of weaned piglets. The age of wean could be forward to 21 days old according to the final body weight of weaned piglets when fed milk replacer supplementation.     

哺乳期补饲代乳品对仔猪生长性能、营养物质消化率及血清生化指标的影响

试验旨在研究哺乳期补饲代乳品对仔猪生长性能、营养物质消化率及血清生化指标的影响,并探讨代乳品对缩短仔猪断奶日龄的可行性。选用120头（12窝）5日龄、平均体重（3.12±0.63）kg的仔猪,随机分为两组,每组60头（6窝,每窝为1个重复）。对照组补饲教槽料至28日龄断奶;试验组补饲代乳品和教槽料（代乳品：教槽料=1：1）至21日龄断奶,断奶后继续饲喂代乳品和教槽料至28日龄;28日龄后试验组和对照组饲喂相同日粮至70日龄。结果显示：①整个试验期,两组仔猪在5、21、28和70日龄时体重差异均不显著（P>0.05）;在5~21、22~28和5~28日龄阶段,试验组仔猪平均日采食量（ADFI）和料重比（F/G）均极显著或显著高于对照组（P < 0.01;P < 0.05）;而在22~28日龄阶段,试验组平均日增重（ADG）极显著低于对照组（P<0.01）。②试验组仔猪保育期的日粮总能（GE）、干物质（DM）、有机物（OM）和粗脂肪（EE）的消化率均显著高于对照组（P<0.05）。③在70日龄时,两组仔猪各项血清生化指标均无显著差异（P>0.05）。结果提示,补饲代乳品可显著增加哺乳期仔猪的采食量,同时促进保育期仔猪对日粮中营养物质的消化吸收。从保育期末体重来看,哺乳期补饲代乳品的仔猪提前至21日龄断奶是可行的。     

The experimental reproduction of thrombocytopenic purpura in piglets.

Two gilts, non-affected members of a litter which had been affected with thrombocytopenic purpura were mated to a boar which was an affected member of the same litter. During pregnancy the gilts were injected with pure thrombocyte suspensions from the boar. Antibodies to the boar's thrombocytes were demonstrated in the sera of both gilts and also in samples of their colostrum at each parturition. The piglets produced from these matings had normal thrombocyte counts at birth but a proportion of them developed thrombocytopenia and purpura similar to that seen in natural cases within a few hours of receiving colostrum. However, despite the fact that this condition was observed in three litters from each of the gilts, a secondary thrombocytopenia at 10 to 14 days of age, characteristic of the naturally occurring condition, was only observed in two piglets in one litter.     

荣昌乳仔猪小肠黏膜二糖酶活性发育规律及影响因素的研究

为了系统研究荣昌乳仔猪二糖酶的发育规律,为荣昌乳仔猪饲养工艺研究及产业化示范优化补料技术提供理论依据,试验选择30窝胎次、产仔数一致的荣昌乳仔猪随机分为补饲(A)组和非补饲(B)组,A组从6日龄开始补饲,B组不补饲,分别在第0,2,5,8,11,15,19,23,28,30,35天取仔猪十二指肠、空肠(前、中、后各段)、回肠测定麦芽糖酶、乳糖酶、蔗糖酶的活性。结果表明:补饲对小肠中3种二糖酶活性有一定的影响,补饲组乳糖酶活性在空肠段8,11,15天显著高于其他各天(P<0.05),蔗糖酶活性在空肠前段和中段11,15天显著高于其他各天(P<0.05);非补饲组麦芽糖酶在十二指肠19天、空肠前段19,15,28天显著高于其他各天(P<0.05),乳糖酶活性在十二指肠15天、空肠前段和中段15,11天显著高于其他各天(P<0.05)。说明乳仔猪进行补饲能提前二糖酶发挥高活性的时间;21日龄断奶二糖酶活性对补饲仔猪的影响小于非补饲组;21日龄断奶仔猪比28日龄断奶仔猪酶活性的波动更大;乳仔猪乳糖酶活性在8,11,15日龄达到较高水平。     

Development of Post‐weaning Diarrhoea in Piglets. Relation to Presence of Escherichia coli Strains and Rotavirus

Weaning of piglets complicated with an exposure to pathogenic strains of Escherichia coli was scrutinized in two sets. The first set comprised 20 animals representing two litters and the second set included 30 animals from five litters. The piglets were either left as controls or exposed to one or three pathogenic strains of E. coli. Aiming to simulate a natural exposure the challenge strains were spread on the floor of the pens at weaning. In addition the pigs experienced several non‐infectious stress factors commonly occurring at that occasion. Some groups were given adrenocorticotropic hormone (ACTH), aiming to simulate a stressful weaning. The balance and the composition of the faecal coliform populations, measured by a metabolic fingerprinting method, was disturbed among all animals following weaning. This disturbance was more pronounced and lasted longer among piglets exposed to pathogenic strains of E. coli. All piglets exposed to pathogenic E. coli shed these strains in faeces. Diarrhoea was induced in the groups exposed to E. coli, but not among the control animals. Pigs not treated with ACTH and subjected to a single pathogenic strain of E. coli became infected but did not develop diarrhoea unless if coinciding with shed of rotavirus. Control pigs excreting rotavirus had no diarrhoea. Diarrhoea was most frequent in the groups exposed to three pathogenic strains of E. coli, and in these groups diarrhoea was seen in the absence of rotavirus. ACTH administration amplified the clinical signs. The litter of origin influenced the development of post‐weaning diarrhoea.     

Evaluation of an atrophic rhinitis vaccine under controlled conditions.

A vaccine containing inactivated cultures of Bordetella bronchiseptica, toxigenic Pasteurella multocida type D and dermonecrotic P multocida type D toxoid in an oil-in-water adjuvant was given to seven sows, with seven others acting as controls. Half the piglets in each litter were exposed intranasally when four days old to B bronchiseptica and when eight days old to toxigenic P multocida type D. There was considerably less sneezing in the litters of the vaccinated sows and when the piglets were 10 weeks old, only 18 per cent had deformed snouts compared with 74 per cent in the litters of the control sows. The average liveweight gain of the piglets born to vaccinated sows was significantly better (P less than 0.05) between two and 10 weeks of age than that of the piglets born to unvaccinated sows, although there were no significant lower respiratory tract lesions in either group. The conchal atrophy scores were significantly lower (P less than 0.001) in the piglets from the vaccinated sows and were negatively correlated (r = -0.37) with increasing liveweight gain. In the liters of the vaccinated sows, P multocida was not isolated from the nasal passages of the in-contact piglets and from only 7 per cent of those deliberately exposed compared with 65 per cent and 79 per cent, respectively, in the litters of the control sows. P multocida was isolated post mortem from the tonsils of 23 per cent of the piglets of vaccinated sows and from 87 per cent of those from unvaccinated sows.     

Prevalence of congenital abnormalities in pigs

The prevalence of congenital defects in piglets in a large intensive piggery was determined by autopsy examination of piglets dying in the first week of life and from records kept by the farm staff. A total of 1908 piglets was examined at autopsy and 14,535 were born over the period of the survey. The prevalence of defects on this farm was estimated to be 2.9% of all piglets born, and at least one piglet with a congenital defect was found in 17.4% of litters. Of the piglets dying in the first week 9.5% had a defect and of these 8% had multiple anomalies. The mean litter size at birth for litters with a malformed piglet was 10.9 compared with 9.9 for litters without a malformed piglet. The total preweaning loss in litters containing a malformed pig was higher (29.8%) than that in litters without malformations (17.4%). The antepartum and parturient deaths in litters with a malformed piglet were 35% higher than normal litters. Parturient and anteparturient deaths amounted to 7.5% of piglets born and the total preweaning mortality was 19.9%. Sixty-six per cent of these mortalities occurred within the first week of life. The litter size at birth increased with parity as did the prevalence of litters containing malformed piglets. Neonatal loss was about 2 pigs per litter for all parities. Litter size at birth in litters containing a malformed pig was consistently higher by one pig per litter from all parities, but parturient (7.1%) and anteparturient (1.4%) deaths were also higher in these litters than in litters without malformations (5.1% and 1.2% respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Neonatal-piglet weight variation and its relation to pre-weaning mortality and weight gain on commercial farms

To determine the effect of within-litter neonatal-weight variation on pre-weaning mortality and weight gain, we analyzed piglet survival and weight gain within 400 litters from 10 commercial farms. Neonatal-weight variation (independent of mean neonatal weight, litter size and sow parity) was associated with pre-weaning survival and weaning-weight variation-but not with mean weaning weight. Neonatal piglets with weights well below the range of most of the litter (low-birth-weight piglets) had an increased risk of dying and were unable to obtain normal weight gains by weaning if they survived. These piglets experienced lower survival and poorer weight gain in larger litters. These piglets also tended to have lower survival but normal (albeit low) weaning weights if they survived in litters from middle-aged and old sows. High neonatal-weight variation resulted in lower survival and more variable weaning weights. Small piglets had a greater risk for poor survival and weight gain compared to their heavier litter-mates (a disadvantage that was exacerbated in large litters).