Neospora abortion epidemic in a dairy herd

Neospora caninrm is a protozoan closely related to Toxoplasma gonclii. It was discovered only a few years ago, but it is now recognised as one of the most common and important causes of abortion in cattle. Brain lesions characteristic of Neospora infection have been found in about 25% of aborted foetuses submitted to diagnostic laboratories in New Zealand and overseas⁽¹⁾⁽²⁾. Average abortion rates due to Neospora on New Zealand farms have been estimated at 7% of pregnancies compared with 4% due to other causes⁽¹⁾. The upper range of abortion rates for Neospora was 17–30% compared to only 7–10% for other causes, showing that the economic effects of Neospora abortions on the more severely affected farms can be devastating.     

Spread of bovine syncytial virus in a dairy herd over a two year period

During a two year period the spread of bovine syncytial virus was monitored in a closed herd of 50 to 100 milking cows. Out of a nucleus of 49 nonpregnant and pregnant heifers, six were found to be infected with bovine syncytial virus. Virus was detected only in the progeny of infected cows and not in the progeny of uninfected animals. Nineteen progeny of the bovine syncytial virus infected cows were studied in detail and virus was isolated from only four. Horizontal spread of the virus did not occur.     

Epizootic of external and internal abscesses in a large goat herd over a 16-year period

From 1973 through 1988, 518 external and internal abscesses were diagnosed in a large commercial goat herd. Of the 518 abscesses, 238 were primary and 280 were secondary abscesses in the same or other anatomic locations. During this period, the herd varied in size from 94 goats in 1973 to 431 goats in 1988. Abscesses in the jaw area were detected in 141 goats, 4 of which developed osteomyelitis of the mandible. Sternal abscesses were detected in 72 goats, with 2 also having osteomyelitis of the sternum diagnosed at necropsy. Most of the abscesses were in the jaw, sternal, facial, and cervical areas. Lung abscesses were diagnosed at necropsy in 20 goats that most recently had 1 or more superficial abscesses. Abscess incidence was 27.6% (112 of 406) in wethers and 22.9% (154 of 687) in does. Actinomyces pyogenes was isolated most frequently by bacteriologic culture of abscess specimens and about 3 times as often as was Corynebacterium pseudotuberculosis or Staphylococcus sp, usually coagulase-positive S aureus. Bacteriologic culture of blood samples, taken during abscess episodes, yielded A pyogenes (n = 3) or C pseudotuberculosis (n = 1) in 3 goats. Results of antibiotic treatment of abscesses were disappointing, with little evidence of altering the course of the disease or sterilizing the abscess, despite the fact that the bacteria were susceptible in vitro to the antibiotics used. Excision of intact abscesses was the preferred treatment for abscesses of the jaw and facial areas.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serological study of a dairy herd with a recent history of Neospora abortion

HERD HISTORY: A cluster of 19 abortions occurred in April and May 1994 on a seasonal dairy farm of 277 cows in Taranaki. Lesions consistent with neosporosis were seen in several foetuses. The age of the aborting cows ranged from 2 to 12 years. Pregnant rising 2-year-old heifers had been grazed off the main farm on a run-off' until returning in May, when they were replaced on the run-off by the rising l-year-old calves. None of these pregnant heifers aborted. METHODS: Sera were obtained from all calves (n = 32), 32 of 33 pregnant heifers, 59 of 60 3-4 year-old cows and 101 of 150 older cows, plus all cows that had aborted. Sera were tested using an indirect fluorescent antibody assay. Non-aborting cattle sera were screened at 1:400, and further dilutions were tested from 15 aborted cows. RESULTS: The percentages of seropositive cattle were: 32% of the calves, 3% of the heifers, 31% of the younger cows and 27% of the older cows. The proportion of seropositive heifers was significantly lower (p< 0.01) than in the other age classes. There was no significant difference in the proportion of seropositive animals between these other age classes (p >0.05). Of the 15 cows that aborted, and for which further dilutions were tested, nine had titres of 1: 12,800, four had titres of 1:6400, one had a titre of 1: 1600 and one had a titre of 1:400. Twenty cows were the dams of pregnant heifers. Six of these cows were seropositive but all their offspring were seronegative. Fifteen aborting cows were held over to the following year when 13 became pregnant and calved normally. There were only two to three abortions in the whole herd in this following year. CONCLUSION: These results suggest that either a point-infection occurred sometime in early 1994 with an infective period short enough so that the heifers did not get infected when they returned to the main farm, or some factor precipitated a recrudescence of latent infection with a subsequent rise in titres in about 29% of the animals on. the main farm only. Although neither hypothesis can be proven or disproven in this observational study, the former hypothesis seems more likely.     

Frequency and causes of infectious abortion in a dairy herd in Queretaro, Mexico

The objective of this study was to determine the frequency of infectious bovine abortion and to identify some of its causes, specifically brucellosis, leptospirosis, bovine viral diarrhea, infectious bovine rhinotracheitis, and neosporosis. The study was carried out in a dairy herd in the state of Queretaro, Mexico, between September 2002 and March 2003. At the beginning of the study, blood samples were taken from a random 33% of the 300 lactating or pregnant cows; antibodies against Leptospira interrogans were the most commonly identified, in 91% of the 99 samples. Blood samples were also taken 14 to 28 d after the 26 subsequent abortions in the herd in the 6-mo study period, as well as from 22 cows that had not aborted within 5 d after the abortions in the other group. Seroconversion was most frequent for L. hardjo, occurring in 8 (67%) of the 12 dams that aborted after the initial serologic sampling and for which paired serum samples were therefore available. Of the 16 collected fetuses, 10 had histologic lesions suggesting infection in various organs, the features correlating with the serologic results for the dams in 7 cases. Thus, the abortions may have been caused by more than 1 infectious agent.     

Seroprevalence of Neospora caninum infection following an abortion outbreak in a dairy cattle herd

OBJECTIVE: To investigate the seroprevalence of Neospora caninum infection in a commercial dairy cattle herd, 15 months after detection of an abortion outbreak. PROCEDURE: Sera from the whole herd (n = 266) were examined for N caninum antibodies by indirect fluorescent antibody test (IFAT) and immunoblot analysis. Herd records were reviewed to collate serological results with abortion history, proximity to calving, and pedigree data. RESULTS: The seroprevalence of N caninum infection was 24% (63/266) for IFAT titre > or = 160, 29% (78/266) for immunoblot positive (+ve), and 31% (82/266) for IFAT > or = 160 and/or immunoblot +ve; 94% (59/63) of animals with IFAT > or = 160 were immunoblot +ve. The association between seropositivity (IFAT > or = 160 and/or immunoblot +ve) and history of abortion was highly significant (P < 0.001); the seroprevalence was 86% (18/21) in aborting cows, compared with 30% (50/164) in non-aborting animals. The abortion rate for seropositive cows was 26% (18/68) compared with 3% (3/117) for seronegative animals. IFAT titres of infected cows were higher within 2 months of calving than at other times (P < 0.001). The association between seropositivity in dams and daughters was highly significant (P = 0.009). CONCLUSIONS: The abortions were associated with N caninum infection and there was evidence of reactivation of latent infection close to calving and congenital transmission of infection. Immunodominant antigens identified by immunoblots may prove useful for improved diagnostic tests.     

Caprine herpesvirus- 1 abortion storm in a goat herd in Quebec

Numerous abortions were reported on a Quebec goat farm, and caprine herpesvirus-1 (CapHV-1) was confirmed by PCR in several tissues from 3 aborted fetuses. This is the first report of CapHV-1 in Canada. Practitioners and diagnosticians must consider this disease when making a differential diagnosis for caprine abortion.     

Terbufos poisoning in a dairy herd

This report describes the accidental poisoning of over 200 head of Holstein cattle by the organophosphate, terbufos. The ingestion of an acutely toxic dose (approximately 7.5 mg/kg) of terbufos by 84 heifers resulted in severe respiratory distress as the primary clinical sign and death within 12 hours. There was no response to treatment with atropine sulfate. One hundred and twenty milking cows received a portion of the contaminated feed diluted approximately ten times. These cattle had typical signs of organophosphate poisoning and responded to atropine sulfate. Severely affected cows received pralidoxime chloride and activated carbon 48 h after terbufos ingestion but did not respond to the drugs. Diagnosis of organophosphate poisoning was confirmed by tissue and feed analysis for terbufos and measurement of whole blood cholinesterase activity.     

Monensin toxicosis in a dairy herd

An acute onset of illness was reported in a lactating dairy herd in Canada in which monensin had been incorporated in error in its ration at almost 10 times the prescribed level. All of the lactating cows became lethargic, were inappetant, developed diarrhea, and had decreased milk production from 28 kg/cow/day, the day before exposure, to 23 kg/cow/day, 3 d later. Within 9 d, all animals recovered from the incident and milk production returned to previous levels.     

Phosphorus deficiency in a dairy herd

Phosphorus deficiency was diagnosed in a 90 cow seasonal supply dairy herd which showed low milk production, ill-thrift, infertility and osteophagia. Serum inorganic phosphorus and pasture phosphorus levels were low, pasture Ca:P ratios high and soil phosphorus levels very low; the soil phosphate retention value was 96%. The deficiency, which had probably existed for several years, was considered to be due to inadequate annual phosphate fertiliser applications on a high phosphate retaining soil. Phosphorus deficiency may have been exacerbated by the application of lime without phosphate several months before the onset of severe clinical disease. The finding of low sodium levels in pasture samples suggested that sodium deficiency may have co-existed and contributed to the clinical picture. Treatment, comprising bone flour dusting of pasture, water trough supplementation and phosphorus-containing injections, appeared to induce ovarian activity in anoestrous cows and suppress osteophagia, though controlled treatment trials were not performed. No improvement was noted in milk production or cow condition. Increased annual super-phosphate and reduced potassium applications were recommended, together with the monitoring of pasture and soil macro elements and serum phosphorus levels. A decision on whether to supplement with sodium would be based on the results of pasture monitoring, since a direct animal test is not currently available. It is suggested that phosphorus deficiency may not be uncommon in dairy herds in some North Island districts; based on the present case, the decline in New Zealand superphosphate quality in the 1970's and recently published data which has shown a high proportion of pasture phosphorus deficient sites in some North Island areas.     

Mycoplasmal mastitis in a dairy herd

In October 1985, mycoplasmas were isolated from bulk tank milk samples in a large Florida dairy (greater than 1,400 lactating cows). At that time, measures to isolate and control the spread of infection were instituted. In an initial screening test, Mycoplasma bovis was isolated from 21 of 153 milking string samples (milk from all quarters of 10 cows/string). Composite quarter milk samples from all quarters of every individual lactating cow in the herd were obtained for culture in November 1985 and December 1985. In October, 88 of 1,535 (5.7%) cows were identified as Mycoplasma-positive. An additional 31 Mycoplasma-infected cows were identified in December. The dairy elected to maintain the infected cows in a separate Mycoplasma-positive subherd, which would be milked at the end of each milking session. Seven additional Mycoplasma-positive cows were identified at initiation of lactation. All newly identified infected cows were transferred to the Mycoplasma-positive subherd. After segregation of Mycoplasma-positive cows, bulk tank milk samples obtained routinely from the main herd remained culture negative throughout the study. From February 1986 to October 1986, quarter milk samples were obtained monthly from cows in the Mycoplasma-positive subherd. Any cow that developed clinical mastitis or substantial decrease in milk production was, at the discretion of the herdsman, culled. Of the 126 cows in the subherd, 22 (17.5%) were culled for mastitis, 35 (27.8%) were culled for low production, and 9 (7.1%) were culled for other reasons. Of the remaining 60 cows, 16 (12.7% of the 126 cows) were Mycoplasma-positive on the basis of results from one or more samples obtained after February 1986.(ABSTRACT TRUNCATED AT 250 WORDS)