Diagnostic characterization of a feral swine herd enzootically infected with Brucella.

Eighty feral swine were trapped from a herd that had been documented to be seropositive for Brucella and which had been used for Brucella abortus RB51 vaccine trials on a 7,100-hectare tract of land in South Carolina. The animals were euthanized and complete necropsies were performed. Samples were taken for histopathology, Brucella culture, and Brucella serology. Brucella was cultured from 62 (77.5%) animals. Brucella suis was isolated from 55 animals (68.8%), and all isolates were biovar 1. Brucella abortus was isolated from 28 animals (35.0%), and isolates included field strain biovar 1 (21 animals; 26.3%), vaccine strain Brucella abortus S19 (8 animals, 10.0%), and vaccine strain Brucella abortus RB51 (6 animals, 7.5%). Males were significantly more likely to be culture positive than females (92.9% vs. 60.6%). Thirty-nine animals (48.8%) were seropositive. Males also had a significantly higher seropositivity rate than females (61.9% vs. 34.2%). The relative sensitivity rates were significantly higher for the standard tube test (44.6%) and fluorescence polarization assay (42.6%) than the card agglutination test (13.1%). Lesions consistent with Brucella infection were commonly found in the animals surveyed and included inflammatory lesions of the lymph nodes, liver, kidney, and male reproductive organs, which ranged from lymphoplasmacytic to pyogranulomatous with necrosis. This is the first report of an apparent enzootic Brucella abortus infection in a feral swine herd suggesting that feral swine may serve as a reservoir of infection for Brucella abortus as well as Brucella suis for domestic livestock.     

Chlamydial infection and perinatal mortality in a swine herd

Chlamydia psittaci was believed responsible for an episode of high perinatal death loss in a swine herd in which 8.5 pigs per litter normally were weaned. In this episode, 18 sows produced 186 pigs, with 50 survivors. Chlamydia was found in tissue samples, and other bacterial or viral pathogens could not be identified. Chlamydia was diagnosed by isolation (ELISA), histologic examination using immunoperoxidase staining techniques, and electron microscopy. Previously, C psittaci has not been considered in the differential diagnosis of swine perinatal mortality.     

Impacts on conceptus survival in a commercial swine herd

An estimated 30 to 40% of potential piglets are lost before farrowing in U.S. or European pig breeds. Because these studies were conducted in limited numbers of university research herds, we decided to characterize the timing, pattern, and extent of conceptus loss in a commercial swine herd in Iowa (Pig Improvement Company; Camborough Line). Sows (parities 2 to 14) were slaughtered on d 25 (n = 83), 36 (n = 78), or 44 (n = 83) of gestation. These days coincide with periods before, during, and after uterine capacity becomes limiting to conceptus survival. At slaughter, numbers of corpora lutea (CL) and uterine horn length were determined, and conceptuses were removed and evaluated. Uterine horn length and CL number did not differ among these days of gestation, averaging 217 cm and 26.6 CL, respectively. In contrast, numbers of conceptuses decreased (P < 0.05) from 15.8 on d 25 to 12.9 on d 36, then remained relatively constant through d 44 (12.1). Thus, conceptus survival averaged 60.2% on d 25, 50.1% on d 36, and 46.3% on d 44, based on numbers of CL present. There was a positive correlation (P < 0.001; r = 0.50) between numbers of viable conceptuses on d 25 and ovulation rate, but this association was completely lost by d 36 (P > 0.10) when uterine capacity becomes limiting. In agreement with this premise, uterine horn length and conceptus number were not associated on d 25 but exhibited positive correlations (P < 0.05) on d 36 (r = 0.36) and d 44 (r = 0.40). On all 3 d examined, the numbers of viable conceptuses were not associated with fetal weight but were negatively correlated (P < 0.05) with placental weight. Compared with the commonly reported values for ovulation rate and percentage conceptus loss in university research herds, values from these production animals were extremely high. Data suggest that throughout this period, larger litters were associated with conceptuses exhibiting small placentae. These data lend support to the concept that increased placental efficiency (fetal weight/placental weight) may contribute to increased litter size in the pig.     

Epidemiology of Pasteurella multocida in a farrow-to-finish swine herd.

Thirty-eight clinical isolates of Pasteurella multocida, recovered from a continuous flow, farrow-to-finish swine herd, were characterized by capsular serotyping and restriction endonuclease analysis (REA) in order to study the epidemiology of P. multocida pneumonia. Twenty-three of the 38 isolates obtained in the study belonged to serotype A. They displayed three REA patterns after digestion with HpaII, of which one designated A-3 represented 70% of the samples. The remaining 15 isolates were serotype D. Four different REA patterns were observed in the type D isolates. The REA type D-1 was most prevalent and accounted for 47% of the serotype D isolates. All serotype A isolates were nontoxigenic, whereas five (33%) of the serotype D isolates were toxigenic. Vertical transmission of P. multocida could not be demonstrated, and was probably not a major route of infection. The results of this study suggest that strains of P. multocida virulent for pigs exist and cause swine pneumonic pasteurellosis in continuous flow herds by horizontal transmission.     

Environmental source of mycobacteriosis in a California swine herd.

Between July 1985 and April 1986, mycobacterial lymphadenitis was recorded in six of 2407 slaughter pigs from a commercial swine herd in which the majority of pigs were raised in confinement. Records showed that all six affected pigs had access to dirt-floored pens at least 81 days prior to slaughter. The mycobacteriosis lesion rate for pigs exposed to dirt pens was 9.4% while in nonexposed pigs the lesion rate was zero. The risk associated with movement of pigs from concrete floored pens to dirt pens was evaluated by a field trial. In the field trial, two litters (5 of 15 pigs) exposed to dirt pens at 12-24 days of age but none of nine nonexposed litters (39 pigs) developed lesions. Mycobacterium avium-complex bacteria were recovered from both exposed litters (9 of 15 pigs) but from none of nine nonexposed litters. Serovars of M. avium-complex isolated from trial pigs included 1, 4, 8, 9, the dual serovar 4/8, and an untypable serovar. Incense-cedar bark (Calocedrus decurrens) used as a flooring material in the pens was demonstrated to be a potential source of M. avium-complex serovar 9. The dual serovar 4/8 and an untypable M. avium-complex were isolated from the dirt-floored pens. No evidence of cross-transmission of M. avium-complex infection was detected. The sporadic pattern of mycobacteriosis observed in the herd probably resulted from infrequent exposure to a common environmental source.     

我国猪群健康管理体系的构建

新中国成立以来,养猪业在我国得到了较快发展,我国城镇居民人均猪肉消费量由1957年的6.72千克升至2007年的18.21千克,我国的猪肉产量由1983年的1 316.1万吨升至2007年的4 287.8万吨。特别值得一提的是,我国农村居民肉类消费的增长更快,猪肉消费占居民消费的比重较高,我国猪的饲养量占世界总饲养量的一半,由此可见,养猪业在我国农业中的地位举足轻重。     

Dwarfism in a swine herd: suspected vitamin A toxicosis

Dwarfism was observed in a group of 30 crossbred pigs. Affected pigs had short limbs and retarded growth. Reduced long-bone length as well as flattening and caudal rotation of the humeral head and the distal femoral condyles were seen at necropsy. Metaphyseal growth plates in vertebrae were narrow and, in long bones, were closed prematurely. There was a sparing of growth plates in traction epiphyses. Vitamin A toxicosis was considered as a possible cause.     

Cottonseed meal (gossypol) toxicosis in a swine herd

Cottonseed meal (CSM) that contained a high concentration of free gossypol was inadvertently used as a protein supplement, without appropriate iron supplementation, for a swine herd in Illinois. Fifty percent of 300 grower and finishing swine died, and an additional 20% became ill during a 4- to 6-week period. Clinical signs included respiratory distress and abdominal distention. At necropsy, the hearts were diffusely pale, flaccid, and rounded because of dilatation of all 4 chambers, the livers were large and congested, and hydropericardium, hydrothorax, and ascites were evident. Histologic changes consisted of diffuse myocardial fiber atropy with perinuclear vacuolation, and multifocal myocardial and skeletal muscle necrosis. Changes in the liver included marked centrilobular congestion, loss of hepatocytes, and fatty degeneration. Differential diagnoses included monensin, selenium, and gossypol toxicoses, and vitamin E/selenium deficiency. Analyzed feed samples did not contain monensin. Feed selenium concentrations ranged from 428 to 1,513 micrograms/kg, and iron concentrations from 160 to 180 mg/kg. Cottonseed meal (3 to 10%) was detected by feed microscopy. A sample of the 40% protein supplement contained 19% CSM and 1,300 mg of free gossypol/kg, whereas feed samples contained 200 to 400 mg of free gossypol/kg. The history, clinical signs, pathologic findings, and feed analyses were compatible with a diagnosis of gossypol toxicosis. Cottonseed meal, a high-protein supplement used widely in southern United States, may contain gossypol (a polyphenolic binaphthalene pigment), which in its free form is especially toxic to simple-stomached animals. If CSM is used, supplementation with ferrous sulfate is recommended at a 1:1 weight ratio with free gossypol, up to 400 mg of FeSO4/kg.     

Brucella suis biovar 3 infection in a Kentucky swine herd

Sows from a large farrow-to-finish operation in western Kentucky had late-term abortions. Boars and breeding-age sows were tested serologically for brucellosis, and 83 of 125 were classified as reactors. No brucellae were isolated from the tissues of 6 unbred reactor sows, but Brucella suis biovar 3 was recovered from 5 aborted fetuses. Epidemiological studies failed to determine the source of the infection.     

Reproductive consequences of an X-autosome translocation in a swine herd.

A survey was conducted on the chromosome makeup and breeding data of pigs housed at the Arkell Research Station, University of Guelph, to determine the reproductive impact of a reciprocal translocation previously identified as t(Xp+;14q-). Blood samples were cultured and chromosome spreads were examined to identify carriers in the herd. Gonadal features of carrier boars and piglets and their age-matched normal counterparts were studied, and the reproductive history of carrier sows, including the number of breedings required for conception, mean litter size, prevalence of still births and malformations, and sex distribution among the piglets, was compared with that of normal (noncarrier) sows. Our observations on testicular histology confirmed that X-autosome translocation-carrier boars are sterile, and the analysis of reproductive data showed that the most striking effects of t(Xp+;14q-) on sows are the 50% increase in the number of breedings required for conception and the over 25% reduction in litter size compared with that of normal sows. The reproductive impact of this and similar translocations on the herd and on the swine industry in general is discussed.     

Congenital meningocele-encephalocele in an experimental swine herd

Fourteen instances of meningocele-encephalocele in an experimental herd were recorded over a 5-year period. Thirteen of these affected animals were subjected to extensive pedigree analyses. Familial associations were strong, and clearly the meningocele-encephalocele in this herd was under genetic influence. However, additional studies are needed to clarify the mode of inheritance and, perhaps, to identify other factors that might be involved.     

Economic assessment of a pseudorabies epizootic, breeding herd removal/repopulation, and downtime in a commercial swine herd

The effect of pseudorabies in a 150-sow farrow-to-finish operation on selected production and economic values was estimated. Mean litter size remained the same throughout the observation period; however, there was a 2-fold increase in suckling pig mortality and a 3.5-fold increase in stillbirths when the months of the epizootic were compared with pre-epizootic months. Following the epizootic, suckling pig mortality was 13.7% greater (P less than 0.05) than that observed in the months preceding the epizootic, whereas stillbirth rate was 71% higher (P less than 0.01) than that reported in the pre-epizootic months. Total net loss for this operation was estimated at +48,175. The major economic losses (approximately 88% of the total loss) were related to breeding herd removal/repopulation and production downtime.     

无需全群淘汰从肥育猪群中根除猪肺炎支原体

利用疫苗和药物,不需要将猪群全部淘汰将猪肺炎支原体从肥育猪群中根除。对3 243头来自猪肺炎支原体阴性猪群的保育猪在被转入猪肺炎支原体阳性肥育猪群前一次性注射灭活疫苗。在第1群已免疫的猪肺炎支原体阴性猪群被转入猪肺炎支原体阳性猪群时,对阳性猪群使用抗生素类药物。所有猪群按猪舍采用全进全出方法进行管理,猪舍内通风和清粪采用单独的处理系统。之后猪场只从猪肺炎支原体阴性母猪群所生产且没做疫苗免疫的仔猪群引猪。血清学调查结果显示,5年半无猪肺炎支原体抗体阳性。结论:这项无需使用全部淘汰方法建立无猪肺炎支原体猪群的根除计划已经获得成功。     

Trichinosis in a herd of swine: cannibalism as a major mode of transmission

In a herd of approximately 1,000 hogs, evaluation of muscle specimens collected at various intervals during a 12-year period (1973 to 1985) indicated continuous transmission of Trichinella spiralis. The farm's rat population and the incidence of trichinosis in the rats was high during 1974, but diminished markedly by 1978. In January 1984, a longitudinal investigation, using tracer pigs, was performed to determine whether rodents and/or other wild animals were involved in transmission of T spiralis on this farm. Tracer pigs exposed to rodents and wild animals did not become infected with T spiralis. The rodent population on the farm was small and none of the rodents trapped and examined were found to be infected. Hog cannibalism also was evaluated as a mode of T spiralis transmission. Results of the investigation indicated that hog cannibalism was the mode of transmission for trichinosis in the herd.     

Lightning injury in an outdoor swine herd.

Three pigs, weighing 63 kg-70 kg each, from a group of 8 pigs in an outdoor pen that was struck by lightning were necropsied. All 3 pigs presented with hind limb paralysis. The only lesions identified were multiple fractures of the last (seventh) lumbar vertebral body and first sacral vertebral segment, with dorsal displacement of the sacrum and transection of the distal spinal cord and spinal nerves. Hemorrhages extended from the fracture sites into muscles immediately surrounding the lumbosacral junction and retroperitoneally into the pelvic cavity. These hemorrhages were not clearly visible until the pelvic region was dissected. Lesions commonly found in human lightning-strike victims were not present in these pigs. Because vertebral fractures may be the only lesions and may be grossly subtle in heavily muscled pigs, careful pelvic and vertebral dissection is recommended in cases of suspected lightning strike and electrocution.