Equine epitheliogenesis imperfecta in two american saddlebred foals is a lamina lucida defect.

Necropsy of two American Saddlebred fillies diagnosed with epitheliogenesis imperfecta (EI) revealed missing patches of epithelium of the skin and oral mucosa as well as dental abnormalities. Examination of the digestive tract did not reveal signs of pyloric atresia in either foal. Histopathologic examination revealed separation of the epidermis from the dermis. In both foals a division within the lamina lucida of the basal lamina was observed by transmission electron microscopy. In comparison with an age-specific control, the ultrastructure of intact skin from the EI-affected foals showed abnormal hemidesmosomes, which lacked a subbasal plate. The morphological and ultrastructural defects observed in the EI-affected American Saddlebred foals were similar to those observed in Herlitz junctional epidermolysis bullosa-affected human newborns, which is caused by a defect in one of the subunits of laminin-5. The close similarity of lesions of the human and equine diseases suggests that EI may be caused by a laminin-5 defect.

Scedosporium prolificans infection associated with arthritis and osteomyelitis in a horse.

Scedosporium prolificans was associated with arthritis and degenerative osteomyelitis in a 6-year-old Thoroughbred racehorse. The horse was suspected to have an inflammatory lesion of the interosseous tendon, but treatment had resulted in only a minimal response. Shortly after diagnostic arthrocentesis of the left metacarpophalangeal joint was performed, the joint became severely swollen, and radiography of the area revealed lysis of the distal end of the third metacarpal bone, the proximal sesamoid bones, and the proximal end of the proximal phalanx. The horse did not respond to treatment and was euthanatized. At necropsy, severe erosive arthritis and degenerative osteomyelitis of the left metacarpophalangeal joint were seen. Swab specimens of the ulcerated lesions of the articular cartilage were submitted for microbial culture, and Scedosporium prolificans was isolated. Scedosporium prolificans is a newly recognized opportunistic fungal pathogen of humans and animals. In humans, S prolificans typically causes focal locally invasive infections that primarily involve musculoskeletal tissues; most often, infection is a result of penetrating trauma or surgical incision. In immunocompromised patients, fatal disseminated infection can occur. The fungus is resistant to almost all currently available antimycotic agents.

Continuance of studies on Population S benzimidazole-resistant small strongyles in a Shetland pony herd in Kentucky: effect of pyrantel pamoate (1992-1999).

Research on benzimidazole-resistant Population S small strongyles began in a Shetland pony herd in 1974 at the University of Kentucky and has continued for over 25 years. The present update, for the period 1992-1999, evaluated activity of pyrantel pamoate (PRT) in field tests in the pony herd. Additional critical tests with PRT and oxibendazole (OBZ) were done in foals born in the herd. Activity of PRT was initially excellent in field tests, based on epg/lpg count data, but declined rapidly during the second full year of pyrantel treatments. Critical test data for small strongyles indicated efficacies of PRT were about 60% at the beginning of the present observations and this intermediate level of removal continued throughout the seven-year period except for 1994 (75%). Unusual was the finding that field test epg/lpg data on small strongyles indicated much lower activity of PRT than found in worm count data in critical tests. The previously reported ineffective activity of OBZ on this population of small strongyles continued. Data are presented on prevalence and drug activity on several species of internal parasites besides small strongyles.

Prevalence of selected species of internal parasites in equids at necropsy in central Kentucky (1995-1999).

A survey to determine current prevalence of several species of endoparasites in equids (n=350) at necropsy was conducted at the Livestock Disease Diagnostic Center in central Kentucky (1995-1999). Thelazia lacrymalis were found in 42% of the 1- to 4-year olds (n=132), which was the only age group examined for these parasites. Five- to 30-year olds (n=157), examined for Onchocerca spp. worms/lesions, had a prevalence of 24%. In > or =1-year olds (n=324), the infection rate for Gasterophilus intestinalis was 12% for second instars and 14% for third instars and for Gasterophilus nasalis was 2% for second instars and 2% for third instars. For Anoplocephala perfoliata (n=268 equids), prevalence was 52%. Data were compiled for the equids according to breed, age, sex, month of necropsy, and number of parasites. Arterial lesions caused by migrating Strongylus vulgaris larvae were observed in a low number (3 of 52) of equids. Specific examination for Parascaris equorum revealed that 46% of 13 weanlings and 10% of 20 older horses were infected. Anoplocephala magna were found in one of the weanlings. Compared to previous studies (about 15-25 years ago) in Kentucky, the present survey indicated the genera Onchocerca and Gasterophilus greatly declined but Thelazia, Anoplocephala, and Parascaris did not.

Critical test evaluation (1977-1992) of drug efficacy against endoparasites featuring benzimidazole-resistant small strongyles (population S) in Shetland ponies.

Several compounds (n = 13 single or combinations; most at therapeutic dosages) were evaluated between 1977 and 1992 in critical tests (n = 91) against benzimidazole (BZ) resistant small strongyles (Population S) and several other species of internal parasites in Shetland ponies, mostly under 1 year old. The closed breeding herd, from which the test ponies were selected, had been treated every 8 weeks with cambendazole (CBZ) for 4 years (1974-1978) and oxibendazole (OBZ) for 14 years (1978-1992). Published field test data (1974-1992) on older ponies in the herd showed BZ resistance of small strongyles. Average efficacies in the present critical tests against small strongyles for OBZ (n = 59 animals) were high in early years (95% or higher), but gradually declined to a low of 1% in 1991. Side-resistance of small strongyles was evident in critical tests (n = 1-6/single drug or combination) for several other BZs and a pro-BZ; ivermectin and piperazine were highly active, but pyrantel pamoate exhibited weak activity. BZ resistance was evident for six small strongyle species (Cyathostomum catinatum, Cyathostomum coronatum, Cylicocylus nassatus, Cylicostephanus calicatus, Cylicostephanus goldi, and Cylicostephanus longibursatus). Activity on bots, ascarids, large strongyles, and pinworms was essentially as expected, indicating no drug resistance.

A study (1977-1992) of population dynamics of endoparasites featuring benzimidazole-resistant small strongyles (population S) in Shetland ponies.

Critical tests (91) were done between 1977 and 1992 in Shetland ponies to evaluate drug susceptibility and population dynamics (present paper) of endoparasites. The test ponies, most less than 1 year old, were from a herd where older animals were treated every 8 weeks initially with cambendazole (CBZ) (1974-1978) and then with oxibendazole (OBZ) (1978-1992). Previous field test data (1974-1992) on older ponies in the breeding herd indicated the presence of benzimidazole (BZ) resistant small strongyles. Data on population dynamics from the present critical tests indicated that 28 species of small strongyles persisted over the study period in spite of initial susceptibility and later refractiveness of six species to both CBZ and OBZ. Changes in intensities and other aspects were observed for the six BZ-resistant species (Cyathostomum catinatium, Cyathostomum coronatum, Cylicocyclus nassatus, Cylicostephanus calicatus, Cylicostephanus goldi, and Cylicostephanus longibursatus). Variabilities, some striking, were found in prevalence and intensity in bots, stomach worms, ascarids, eyeworms, large strongyles, pinworms and tapeworms.

Natural superinfection of Parascaris equorum in a stall-confined orphan horse foal.

At 4 days of age, an orphan horse foal born on a pasture was placed in a parasite-free stall. It was euthanized at 205 days of age and examination revealed numerous. Parascaris equorum specimens, ranging from 3.0 mm to adult size, indicating reinfections in the stall over an extended period of time. Initial infection of the foal was from stages on pasture. The foal had been observed repeatedly eating its own feces and the question is posed as to whether "recycling' of P. equorum eggs several times by coprophagy allowed time for embryonation and reinfection to occur.

Resistance of castrated male horses to attempted establishment of the carrier state with equine arteritis virus.

Twelve geldings all became infected when inoculated intranasally with the KY-84 strain of equine arteritis virus (EAV), a strain previously shown to be capable of establishing the carrier state in the stallion. With the exception of one animal that showed no effects other than pyrexia, all of the geldings developed clinical signs characteristic of equine viral arteritis (EVA). The geldings were febrile for varying periods within the range of 2-10 days after inoculation. Viraemia occurred from day 2 onwards, for periods varying from 9 to at least 19 days. Nasal shedding of virus began 2-4 days after inoculation and persisted for periods ranging from 7-14 days. All geldings "seroconverted" to EAV by day 11, with serum neutralization titres ranging from 8 to 64. The titres ranged from 8 to 32 after 4 weeks. Low concentrations of EAV were detected in the kidney and blood of one gelding killed 30 days after inoculation and in the blood of another killed after 57 days. Virus was not isolated from any tissue or fluid sample collected from the remaining 10 geldings, all of which were killed between days 30 and 148. The findings confirm that persistent EAV infection is unlikely to occur in geldings and support the results of previous studies, which demonstrated that testosterone plays an essential role in the establishment and maintenance of the carrier state.

Control of cambendazole-resistant small strongyles (Population S) with oxibendazole in a pony band: an 8 year field test (1984-1992).

Studies in a band of ponies harboring Population S benzimidazole-resistant small strongyles were initiated in 1974 and have continued for 18 years. Treatment (bimonthly) was with cambendazole for the first 4 years and with oxibendazole (OBZ) for the next 14 years. Data on the first 10 years have been published. The present investigation includes the last 8 years (4 October 1984-11 September 1992), which are the seventh through fourteenth years, of treatment with OBZ. Pre- and posttreatment mean counts of strongyle eggs (epg) and larvae (lpg) per gram of feces were determined biweekly during the current study to monitor the efficacy of OBZ. The average annual percent reductions of epg counts effected by OBZ treatments were 51%, 53%, 38%, 38%, 39%, 28%, 40%, and 19% for the seventh through fourteenth years, respectively. Similar levels of reductions were observed for lpg counts. Although OBZ was initially highly effective on this population of small strongyles, epg and lpg counts gradually declined, but have remained more or less constant since the fifth year of research. However, reductions of the counts were the lowest for the last year of the study.

Causes of abortion, stillbirth, and perinatal death in horses: 3,527 cases (1986-1991).

Pathology case records of 3,514 aborted fetuses, stillborn foals, or foals that died < 24 hours after birth and of 13 placentas from mares whose foals were weak or unthrifty at birth were reviewed to determine the cause of abortion, death, or illness. Fetoplacental infection caused by bacteria (n = 628), equine herpesvirus (143), fungi (61), or placentitis (351), in which an etiologic agent could not be defined, was the most common diagnosis. Complications of birth, including neonatal asphyxia, dystocia, or trauma, were the second most common cause of mortality and were diagnosed in 19% of the cases (679). Other common diagnoses were placental edema or premature separation of placenta (249), development of twins (221), contracted foal syndrome (188), other congenital anomalies (160), and umbilical cord abnormalities (121). Less common conditions were placental villous atrophy or body pregnancy (81), fetal diarrhea syndrome (34), and neoplasms or miscellaneous conditions (26). A diagnosis was not established in 16% of the cases seen (585). The study revealed that leptospirosis (78) was an important cause of bacterial abortion in mares, and that infection by a nocardioform actinomycete (45) was an important cause of chronic placentitis.

Equine abortion and stillbirth in central Kentucky during 1988 and 1989 foaling seasons.

Pathologic and microbiologic examinations were performed on 1,211 aborted equine fetuses, stillborn foals, and placentas from premature foals in central Kentucky during the 1988 and 1989 foaling seasons to determine the causes of reproductive loss in the mare. Placentitis (19.4%) and dystocia-perinatal asphyxia (19.5%) were the 2 most important causes of equine reproductive loss. The other causes (in decreasing order) were contracted foal syndrome and other congenital anomalies (8.5%), twinning (6.1%), improper separation of placenta (4.7%), torsion of umbilical cord (4.5%), placental edema (4.3%), equine herpesvirus abortion (3.3%), bacteremia (3.2%), fetal diarrhea (2.7%), other placental disorders (total of 6.0%), and miscellaneous causes (1.6%). A definitive diagnosis was not established in 16.9% of the cases submitted. Streptococcus zooepidemicus, Escherichia coli, Leptospira spp., and a nocardioform actinomycete were organisms most frequently associated with bacterial placentitis, and Aspergillus spp. was the fungus most often noted in mycotic placentitis. No viral placentitis was noticed in this series. Dystocia-perinatal asphyxia was mostly associated with large foals, maiden mares, unattended deliveries, and malpresentations. The results of this study indicate that in central Kentucky, the noninfectious causes of equine reproductive loss outnumber the infectious causes by an approximate ratio of 2:1, placental disorders are slightly more prevalent than nonplacental disorders, Leptospira spp. and a nocardioform actinomycete are 2 new important abortifacient bacteria in the mare, the occurrence of contracted foal syndrome is unusually frequent, the incidence of twin abortion has sharply declined, and torsion of the umbilical cord is an important cause of abortion in the mare.

Leptospirosis in equine fetuses, stillborn foals, and placentas.

Leptospirosis was diagnosed in 51 equine fetuses and 16 stillborn foals with gestational ages from 3 1/2 to 11 months. Diagnosis was based on one or more of the following: positive fetal antibody titer, positive fluorescent antibody test, demonstration of spirochetes in kidney and/or placental sections stained by the Warthin-Starry technique, high leptospiral titers in aborting mares, or isolation of Leptospira spp. from fetal organs. Gross lesions were observed in 80.3% of the fetuses, stillborn foals, and placentas. Gross placental lesions included nodular cystic allantoic masses, edema, areas of necrosis of the chorion, and necrotic mucoid exudate coating the chorion. The liver (23 cases) was enlarged, mottled, and pale to yellow. The kidneys (seven cases) were swollen and edematous with pale white radiating streaks in cortex and medulla. Microscopic lesions were observed in 96% of fetuses, stillborn foals, and placentas. Placental lesions consisted of thrombosis, vasculitis, mixed inflammatory cell infiltration of the stroma and villi, cystic adenomatous hyperplasia of allantoic epithelium, and villous necrosis and calcification. Fetal lesions included hepatocellular dissociation, mixed leukocytic infiltration of the portal triads, giant cell hepatopathy, suppurative and nonsuppurative nephritis, pulmonary hemorrhages, pneumonia, and myocarditis. Spirochetes were demonstrated with the Warthin-Starry stain in the allantochorion and/or kidney of 69 of the 71 cases. Using the direct fluorescent antibody technique, 56/60 cases tested positively for leptospires. Leptospires were isolated from fetal tissues in 20/42 cases. Sixteen of the isolates were identified by restriction enzyme analysis as Leptospira interrogans serogroup Pomona serovar kennewicki; case Nos. 36 and 41 were serovar grippotyphosa.(ABSTRACT TRUNCATED AT 250 WORDS)

Histoplasmosis in horses.

Histoplasmosis was diagnosed in nine horses during 1986-1990. The infection with Histoplasma capsulatum caused granulomatous placentitis and abortion in one mare in the 7th month of gestation and three mares in the 10th month. Four newborn foals died from severe granulomatous pneumonia within a few days of birth; and a weanling thoroughbred developed granulomatous pneumonia and lymphadenitis at 5 months of age.

Adenomatous hyperplasia of equine allantoic epithelium.

Adenomatous hyperplasia with or without cystic formation of allantoic epithelium was observed in 63/954 equine placentas examined from 1 February 1988 to 31 January 1990. In 61/63 placentas, the adenomatous hyperplasia was associated with other placental lesions: 49 with chronic or chronic-active placentitis, six with placental edema, three with fetal diarrhea, one with placentitis and fetal diarrhea, one with fetal diarrhea and placental edema, and one with hyperplasia of chorionic epithelium. When lesions were less severe, the hyperplastic lesions were not grossly visible, but when lesions were severe, nodular, tumorous, cystic masses were observed at or near the insertion site of umbilical blood vessels. Histologically, lesions classified as stage 1 were characterized by hypertrophy and hyperplasia of epithelial cells and formation of intraepithelial glands (lumina). Lesions classified as stage 2 were characterized by the presence of fibro-adenomatous changes in the allantoic stroma. Lesions classified as stage 3 were characterized by the formation of the nodular masses, which were composed of glandular or cystic structures of various sizes lined by cuboidal or low to medium columnar epithelium. These glands or cysts were empty or contained amphophilic secretion, a mixture of neutrophils and secretion material, or neutrophils. The cause of adenomatous hyperplasia of the equine allantois is not certain; however, there is a close connection between chronic placental disorders and this hyperplastic lesion.

Etiology and pathology of equine placentitis.

Placentas from aborted, stillborn, and premature foals were examined during the 1988 and 1989 foaling seasons, and 236 of 954 (24.7%) had placentitis. Microorganisms associated with placentitis were isolated or demonstrated from 162 of 236 (68.6%) placentitis cases. Leptospira spp. and a nocardioform actinomycete were 2 important, newly emerging bacteria associated with equine placentitis. Major pathogens identified in decreasing order were Streptococcus zooepidemicus, Leptospira spp., Escherichia coli, a nocardioform actinomycete, fungi, Pseudomonas aeruginosa, Streptococcus equisimilis, Enterobacter agglomerans, Klebsiella pneumoniae, and alpha-hemolytic Streptococcus. Pathogens were not recovered in 64 cases (27.1%) and overgrowth by saprophytic bacteria was recorded in 10 cases (4.2%). Twenty-seven cases (16.6%) had mixed bacterial growth and 93 cases (57.4%) had bacteria cultured from both placenta and fetal organs. The majority of the placentitis cases caused by bacteria, with the exception of Leptospira spp. and the nocardioform actinomycete, occurred in 2 forms. One was acute, focal or diffuse; had an infiltration of neutrophils in the intervillous spaces or necrosis of chorionic villi; was associated with bacteremia; and frequently occurred in the placenta from fetuses expelled before or at midgestation. The other was observed from foals expelled at late gestation, was mostly chronic and focal or focally extensive, and occurred mostly at the cervical star area. Chronic placentitis was characterized by the presence of 1 or a combination of the following lesions: necrosis of chorionic villi, presence of eosinophilic amorphous material on the chorion, and infiltration of mononuclear inflammatory cells in the intervillous spaces, villous stroma, chorionic stroma, vascular layer, and allantois.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of respiratory infections in horses with ceftiofur sodium.

Ceftiofur sodium was evaluated as a therapy for respiratory infections in horses. This cephalosporin antimicrobial was administered intramuscularly every 24 h and at a dose of 2.2 mg/kg (1.0 mg/lb) of body weight. The efficacy of ceftiofur sodium was compared with that of a positive control drug, ampicillin sodium (recommended dose of 6.6 mg/kg [3 mg/lb], given every 12 h). Both treatments were continued for 48 h after clinical symptoms were no longer evident (maximum of 10 days). Fifty-five (55) horses with naturally acquired respiratory infections were included in the study; 28 were treated with ceftiofur and 27 with ampicillin. Clinical improvement was recorded for 92.9% of the patients treated with ceftiofur and 92.6% of the animals receiving ampicillin. Both therapies reduced body temperatures to an afebrile level after 2 days of treatment. Complete recovery/cure was noted for 78.6% of the ceftiofur patients and 59.3% of the horses treated with ampicillin. Supporting variables (depression/malaise, respiration/dyspnoea, nasal discharge) were assessed and these also substantiated the effectiveness of the treatments. Both antibiotics were well tolerated. Neither pain nor swelling were noted at the ceftiofur injection site(s). None of the animals developed diarrhoea. Data from this study indicated that ceftiofur sodium is an effective and safe treatment for respiratory infections in horses.