A survey of 93 dairy and five beef herds from five regions of the United States revealed that at least one cow in 90% of the herds was seropositive for antibody to Neospora caninum (1). The prevalence of seropositive cattle in these herds was 2 to 65%. With Neospora caninum, seropositive cattle are infected because the organism is persistent and not cleared.
There are several problems that result from having seropositive cows in a herd. The major problem is production losses from decreased milk production and abortion. Independent studies in the United States demonstrated that seropositive cows had decreased milk production of 2.5 lbs./day/cow in one study (2) and 2.8 lbs./day/cow in another study (3) when compared with seronegative cows. In the later study, decreased milk production caused a $128 loss per lactation period/seropositive cow. Another major problem with having seropositive cows in a herd is that vertical transmission occurs. The frequency of vertical transmission varies considerably, but can reach 100% (4). A recent evaluation of economic considerations for diagnostic and control options for Neospora caninum-induced abortion in beef cattle used a 5-year economic simulation model (5). A seroprevalence of 10% in cow-calf herds decreased mean return to fixed assets by 22.2%. The control strategy with the best economic return involved testing the entire herd for antibodies to Neospora caninum and excluding heifers from seropositive cows as replacements (5).
References
1. Rodriguez I, L Choromanski, SJ Rodgers, and D Weinstock. Survey of Neospora caninum antibodies in dairy and beef cattle from five regions of the United States. Vet. Ther. 3:396-401, 2002.
2. Thurmond MC, and SK Hietala. Effect of Neospora caninum infection on milk production in first-lactation dairy cows. J. Am. Vet. Med. Assoc. 210:672-674, 1997.
3. Hernandez J, C Risco, and A Donovan. Association between exposure to Neospora caninum and milk production in dairy cows. J. Am. Vet. Med. Assoc. 219:632-635, 2001.
4. Campero CM, DP Moore, H Lagomarsino, AC Odeon, M Castro, and H Visca. Serological status and abortion rate in progeny obtained by natural service or embryo transfer from Neospora caninum-seropositive cows. J. Vet. Med. B Infect. Dis. Vet. Public Health 50:458-460, 2003.
5. Larson RL, DK Hardin, and VL Pierce. Economic considerations for diagnostic and control options for Neospora caninum-induced abortions in endemically infected herds of beef cattle. J. Am. Vet. Med. Assoc. 224:1597-1604, 2004.
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