Neospora caninum infection and abortion in a dairy herd
A dairy farmer complained of a high frequency of abortion in his herd. As part of the effort to investigate the possible causes of the problem, serum samples were obtained from 90 adult cows randomly selected from all 400 present in the herd and sent to a laboratory for the detection of antibodies against Neospora caninum. Of the 90 cows sampled, 23 (25.56%) were seropositive against the parasite. To further explore the role of N. caninum exposure as a cause of abortion in the herd the farmer was asked to follow the cows during the following year and a half, and record whether they experienced an abortion or not.Use the results in the file smve_tma_1.txt to describe the status of the herd with respect to N. caninum, the frequency of abortions and the relationship between N. caninum exposure and abortion. A data dictionary is provided in the fileSMVE_TMA_data_2015.docx.
In your answer include the following:
- What is the probability that a cow in this herd is positive to N. caninum?
- What is the estimated probability of a cow in this herd aborting?
- What type of epidemiological study are we conducting to assess the relationship between N. caninum exposure and abortion?
- What is the strength of association between exposure to N. caninum and abortion?
- What is the relationship between the different measures of strength of association and which one is more appropriate?
- Is there a significant relationship between exposure to N. caninum and abortion in this herd?
- Is the 'survival probability' for abortion different between seropositive and seronegative cows?
- What is the impact of the exposure on the population (the herd)?