Gross and histopathological findings in unusual lesions caused by Streptococcus suis in pigs. I. Cardiac lesions.

Unusual lesions caused by Streptococcus suis involved the heart of 48 pigs necropsied over a four-year period. Lesions included fibrinopurulent pericarditis (six pigs), hemorrhagic, necrotizing myocarditis resembling mulberry heart disease (21 pigs), and vegetative valvular endocarditis (21 pigs). Histologically, the myocarditis was characterized by focally extensive and diffuse hemorrhages and necrosis, with infiltrations of neutrophils and mononuclear cells, and thrombosis of small and large myocardial vessels. The 21 pigs with vegetative valvular endocarditis generally were over ten weeks old and had died suddenly. The left atrioventricular valve was affected in 18 hearts. Most of an affected valve was replaced by a layer of granulation tissue covered by a mixture of fibrin, inflammatory cells, necrotic debris and large numbers of coccoid bacteria.     

Gross and histopathological findings in unusual lesions caused by Streptococcus suis in pigs. II. Central nervous system lesions.

Subacute meningoencephalitis or meningoencephalomyelitis caused by Streptococcus suis was diagnosed in 53 pigs over a four-year period. Affected pigs averaging 11 weeks of age with a range from five days to 26 weeks, had been treated with antibiotics and had partially recovered. Hyperemia of meningeal vessels and modest increase in cerebrospinal fluid were the most common gross central nervous system lesions. Histologically, fibrin, edema and a mixture of inflammatory cells were present in meninges and choroid plexus. Linear and perivascular infiltrates of neutrophils and mononuclear inflammatory cells invaded the brain and spinal cord and similar infiltrates were in lumina of ventricles and the spinal canal. Inflammatory cells also invaded the superficial layers of the brain directly from the overlying meninges. Bilateral subacute optic perineuritis and Gasserian ganglioneuritis also occurred. Segmental cortical necrosis of cerebellar folia characterized by degeneration, necrosis, neuronophagia and drop out of groups of Purkinje cells was a distinct lesion seen in 27 of the 53 pigs. Mild spongiosis of white matter in the cerebellum and brain stem accompanied these changes.     

Conjunctivitis caused by a swine Chlamydia trachomatis-like organism in gnotobiotic pigs.

The objective of this study was to determine whether a chlamydial strain recovered from growing and finishing swine with conjunctivitis or keratoconjunctivitis could cause the same infections in gnotobiotic pigs. The strain shares biological characteristics with Chlamydia trachomatis. After propagation in Vero cells and preparation of the inoculum (10(7) inclusion-forming units/ml), chlamydial strain H7 was instilled into the ventral conjunctival sac (0.15 ml/sac) of 12 anesthetized 3-day-old gnotobiotic piglets. Four age-matched gnotobiotic piglets were anesthetized and sham infected with uninfected cell culture lysates. None of the principal piglets developed clinical symptoms of conjunctivitis or keratoconjunctivitis. Principal piglets necropsied 7 days postinfection (DPI) had histologic lesions of mild or moderate conjunctivitis; immunohistochemical evaluation revealed chlamydial antigen in conjunctival epithelium. A majority of principal piglets necropsied at 14-28 DPI had histologic lesions of mild conjunctivitis, but chlamydial antigen was not detected by immunohistochemistry. The results indicated that chlamydial strain H7 can cause mild or occasionally moderate conjunctivitis in gnotobiotic pigs, but the conjunctival infection is asymptomatic.     

The aetiology of diarrhoea in pigs weaned at two days of age.

When pigs are weaned at two days of age large numbers of Excherichia coli appear in the anterior gut and the incidence of diarrhoea rises. The two phenomena do not appear to be directly related because the strains of E coli isolated are not serotypes previously found to be associated with neonatal pig scouring. Representative strains of the non-enteropathogenic serotypes did not produce enterotoxin and did not adhere to small intestine brush borders. Moreover when antibiotics were fed to eliminate E coli from the gut, the pigs still scoured. Rotavirus was detected in the gut contents and gut epithelium of scouring pigs and a bacteria-free filtrate of gut contents produced diarrhoea when administered to germ-free pigs. It is suggested that rotavirus may be one of the causes of the scouring seen shortly after weaning pigs at two days of age.     

Factors to adjust litter weight of pigs to a standard 21 days of age

Factors to standardize litter weights of nursing pigs to 21 d of age were calculated from daily weights measured on 64 crossbred litters from 10 to 32 d of age. The results were compared to published factors derived from a data set of Duroc pigs weighed every 3 to 4 d. Dams in the present study were white crossbred sows and gilts, and sires were maternal or terminal breed types. Multiplicative factors were calculated by dividing the mean 21-d litter weight (LW21) by mean daily litter weight. Linear and quadratic regression coefficients of LW21 on age at weighing were fitted to the factors (R2 = .997). The final equation for adjusting litter weights to a 21-d basis was 2.5246 - .1041 x (d of age) + .0015 x (d of age)2. There were good agreement with published factors for d 19 to 25, but divergence for younger and older litters resulted in significant differences between the linear coefficients. These differences may be due to departure from a linear growth curve, which daily measurements would incorporate, or differences in sow populations. Thus, use of the new factors should be considered for white crossbred sow populations. A least squares analysis indicated that LW21 was significantly altered by parity, not by the number of pigs allowed to nurse or by breed of sire. After adjustment to 21 d, litter weights also should be adjusted for differences in parity before evaluating sow productivity, by using additive factors such as those recommended by the National Swine Improvement Federation.     

Liquid diets fed hourly to pigs weaned at 19 days of age and exposed to rotavirus (weanling diarrhea)

Five diets were tested for their capacity to promote weight gains in newly-weaned, 19-d-old, rotavirus-exposed pigs. The diets were tested under conditions designed to minimize the stress of weaning. That is, rotavirus-exposed pigs were moved at weaning to an isolation unit, caged individually and fed hourly liquid diets that were high (approximately 26%) and low in protein (approximately 11%). In all experiments, pigs experienced postweaning rotavirus-associated diarrhea and depression in rate of gain. Pigs grew faster: when fed diets high in protein (approximately 26% protein) vs low in protein (approximately 11% protein) and when fed diets containing cows' milk proteins vs proteins from soybean flour. A diet containing antibodies to rotavirus did not ameliorate the weanling diarrhea.     

Aberrant chlamydial developmental forms in the gastrointestinal tract of pigs spontaneously and experimentally infected with Chlamydia suis

The phenomenon of persistence is well known from in vitro studies, where it is associated with the production of aberrant bodies, but its occurrence in vivo is less well documented. The objective of this study was to search for aberrant bodies in intestinal tissues from pigs, describe their ultrastructure, and investigate the suitability of immunohistochemical staining for chlamydial heat shock protein 60 (cHSP60) to detect such forms. Intestinal tissues derived from pigs naturally and experimentally infected with Chlamydia (C.) suis were examined by immunohistochemistry, transmission electron microscopy and immunogold electron microscopy. The chlamydial species involved in the natural infection were determined using an Array Tube Microarray to C. suis and Chlamydophila abortus. Ultrastructurally, aberrant bodies were detected in the gut of both naturally and experimentally infected pigs. Immunogold electron microscopy showed that the aberrant bodies were labeled less strongly than the normal forms by antibodies against LPS and cHSP60 respectively. It was concluded that aberrant bodies occur in vivo in pigs and that the gnotobiotic pig model might be suitable for the study of chlamydial persistence in vivo. The antibody against cHSP60 does not appear to be suitable to specifically detect such forms.     

Intestinal translocation of Streptococcus suis type 2 EF+ in pigs

Sepsis with subsequent multisystem organ failure after translocation of bacteria from the gut is a serious risk associated with stress situations. We showed that intestinal bacterial translocation could be one of the pathways for pathogenic Streptococcus suis infections in the pig. In 24 piglets weighing 10-14 kg, free of the extracellular factor (EF+) producing phenotype of S. suis serotype 2, a silicon canula was placed in the proximal jejunum to enable intestinal inoculation and bypassing the upper alimentary tract. The pigs were individually housed. After stress induction in 18 pigs by means of a truck drive in individual cages for 1h, pigs were inoculated through the intestinal canula either with S. suis type 2 EF+ or with growth medium only, and put back in their original housing. The six not transported pigs were also inoculated with the same strain. To prevent oral self-infection, faeces were collected in a bag that was glued around the anus. Clinical and behavioral symptoms were recorded for 72 h post inoculation, and then the animals were sacrificed for pathological and bacteriological examination. In three animals, the inoculation strain was re-isolated from mesenterial lymph nodes and typically affected organs. No S. suis type 2 EF+ was detected by specific polymerase chain reaction (PCR) in any of the tonsil-swabs and -homogenates. We concluded that infection of the organs had taken place after bacterial translocation out of the gut and that the intestinal tract can be a porte d'entree for S. suis type 2 EF+.     

Effect of Cryptosporidium baileyi on broilers infected at 26 days of age

Cryptosporidium baileyi causes respiratory disease, pallor, death, and transient increased feed conversion (FC) and decreased body weight gain (BWG) when intratracheally (IT) inoculated into young chicks. Unlike the case for young chicks in previous studies, C. baileyi had no effect on FC, BWG, or mortality in IT-inoculated 26-day-old chicks. Results from two different histologic evaluations indicated that IT inoculation with 10(4) oocysts caused higher epithelium lesion scores (P less than 0.05) and higher mucosal area scores (P less than 0.05) than did IT inoculation with more, fewer, or no oocysts. Reasons for these findings and implications of chicken immune system response to or modulation by C. baileyi are discussed.     

Immunization of pigs against Streptococcus suis serotype 2 infection using a live avirulent strain.

Streptococcus suis capsular type 2 is still an important cause of economic losses in the swine industry. At the present time, vaccination of pigs against this infection is generally carried out with autogenous bacterins and results are equivocal. In this study, the protective effect of a live avirulent S. suis type 2 strain (#1330) which had induced a good protection in mice, was evaluated in swine. The experiment was performed in triplicate using 4 week-old piglets. A total of 15 piglets were vaccinated 3 times, 15 others were vaccinated 2 times, and 15 piglets were injected 3 times with sterile Todd-Hewitt broth. Using an indirect ELISA, an increase in the IgG response to S. suis antigens was noted in 27 of the 30 vaccinated piglets. On day 21 post-vaccination, all animals were challenged intravenously with a virulent S. suis type 2 strain (#999). In the 2 vaccinated groups, 26 animals were fully protected. Only 1 out of the 15 piglets vaccinated 3 times developed mild clinical signs. In the group vaccinated twice, 3 piglets showed clinical signs and 1 of them died after the challenge. In the control group, 7 animals died out of the 11 with clinical signs of infection. In conclusion, a protective immunity was observed in swine when using strain 1330. However, more studies are needed to assess the use of a live S. suis strain in a vaccine for pigs.     

Production performance and pruritic behaviour of pigs naturally infected by Sarcoptes scabiei var. suis in a contact transmission experiment

Reports on the effects of mange on the production performance of pigs are conflicting. So far, studies have used experimental infections, by depositing encrusted lesions from chronically infected pigs into the ears of experimental pigs. However, this is a poor representation of what happens under natural field conditions. The purpose of our study was to quantify the effects of sarcoptic mange on production performance and pruritus in pigs that were infected by contact with S. scabiei var. suis-infected pigs. A total of 80 piglets were matched by sex and weight and randomly divided between experimental and control compartments. In the experimental compartment, each of three naturally S. scabiei var. suis-infested pigs were randomly allocated to three pens with 13 susceptible pigs each. From day 0 to 35, the growth performance of pigs in the experimental compartment was significantly (P=0.04) worse (35 g/d) than of pigs in the control compartment. From day 35 to 112, there was a statistical trend (P=0.10) that the growth performance of pigs in the experimental compartment was lower (50 g/d) than that of pigs in the control compartment. For the complete fattening period (0-112 or more days), the growth performance of pigs in the experimental compartment was significantly (P=0.05) worse (41 g/d) than that of pigs in the control compartment. Mean feed conversion ratio (kg feed per kg gain) was 2% higher in the experimental compartment compared with the control compartment. Pigs in the experimental compartment had a nine times (95% CI: 2 - 44) higher chance of showing pruritic behaviour than pigs in the control compartment.     

Protein-losing enteropathy caused by Lawsonia intracellularis in a weanling foal

A 5-month-old Morgan filly was presented to the Atlantic Veterinary College with a history of lethargy, fever, depression, anorexia, and dependent ventral edema. Diagnostic tests revealed severe inflammation, hypoproteinemia, and thickened small intestinal loops. Protein-losing enteropathy caused by Lawsonia intracellularis was diagnosed and treated successfully with erythromycin-rifampin.     

Intestinal strangulation caused by intra-abdominal lipomas in a dog.

Pedunculated, intra-abdominal lipomas caused intestinal strangulation in a Doberman Pinscher. The dog was treated surgically to remove the lipomas and the devitalized intestine but died soon after surgery. Histologic evaluation confirmed the diagnosis of lipoma.