Q drudža sastopamība slaucamo govju ganāmpulkos Latvijā un tā ietekme uz reprodukcijas rādītājiem = Prevalence of Q fever in dairy herds in Latvia and its influence on reproductive parameters
Authors:   ,   Latvia University of Life Sciences and Technologies, Ringa-Osleja Guna 
Published: March 2024

The doctoral thesis "Prevalence of Q fever in dairy herds in Latvia and its influence on reproductive parameters" by Guna Ringa-Osleja was carried out during the period from 2016 to 2023 at the Clinical Institute of Faculty of Veterinary Medicine, Latvia University of Life Sciences and Technologies and Institute of Food Safety, Animal Health and Environment BIOR. The study was carried out in four activities - the first was to compare productivity and reproductive parameters in both Q fever-affected and non-affected dairy herds in Latvia. The second one was to detect risk factors associated with the incidence of the disease and to detect reproductive parameters in both Q fever-affected and non-affected dairy herds. The third activity was to detect the dynamics of Q fever in dairy herds and its relation to reproductive problems in anamnesis. The fourth activity was to estimate further animal reproduction and productivity after an abortion related to C. burnetii serological response or presence. In the first activity, there were collected and compared data (the number of animals, productivity, somatic cell count, days in milk, the age of the first artificial insemination and calving in heifers, insemination rate, days open and dry period in cows) from 118 dairy herds included in the recording database (58 Q-fever-affected, 60 no-affected). In the second activity, a survey was performed in 58 dairy herds (36 Q-fever-affected, 22 non-affected) to detect risk factors associated with the incidence of the disease and the frequency of reproductive issues for animals at the herd level. Depending on the farms' management, the survey was performed on-site, by phone interview, or electronically. The third activity was carried out in 15 Q-fever-affected herds. In the third activity, the individual sera and milk samples were collected to detect the C. burnetii phase-specific serological response, the typical serological response, and the presence of DNA in milk. Collecting samples twice with intervals of 7-13 months, we detected the dynamics of infection within the herd. The individual samples were collected under the same scheme from randomly selected animals (pregnant heifers, milking cows). We selected two to four animals with previous anamnesis reproductive problems, including multiple inseminations, prolonged cycles, abortion, or stillborn. The other ones were animals of the control group (pregnant heifers, milking cows) without reproductive problems in anamnesis. Repeatedly, samples were collected from the same animals. We estimated C. burnetii's serological response and presence with reproductive problems in anamnesis. In the fourth activity, we collected data about all the aborted animals from five Q-fever-affected dairy herds during the four-year period. We estimated further reproduction and productivity for both C. burnetii-related and non-related aborted animals and compared those data with the medium ones from the herd. The hypothesis of the doctoral thesis: Q fever can impair reproductive parameters in dairy herds significantly, and recognizing the risk factors influencing the incidence of the disease can help limit it. The aim of the doctoral thesis: to detect the presence of Q fever in dairy herds in Latvia and its influence on reproductive parameters Objectives of the doctoral thesis: 1. to identify the typical reproduction and productivity parameters in both Q-fever-affected and non-affected dairy herds by comparing the record data; 2. to identify risk factors influencing the presence of Q fever in the herd and to compare the frequency of reproductive problems by performing a survey in both Q-fever-affected and non-affected dairy herds; 3. to detect the prevalence, changes and dynamics of Q fever by detection of Coxiella burnetii serological response and presence, and relation to reproductive anamnesis; 4. to estimate the further reproductive ability and productivity in animals after an abortion related to Coxiella burnetii. Personal contributions: 1. selection, sorting, and analysis of productivity and reproductive parameters for both Q-fever-affected and non-affected dairy herds selected for the study; 2. the creation of the survey to detect risk factors influencing the prevalence of the disease, including questions about the creation/ improvement/ renewal of the herd, housing, hygiene, and other factors. Questions about a delivery, post-partum diseases, and extra culling during the last year were included to detect the frequency of reproduction-related health parameters. A survey was performed personally in many of the herds. Statistical data processing was performed personally; 3. the individual blood and milk samples were collected personally in most cases, and testing of samples in the laboratory was assisted personally in a few cases. Selection, sorting, and analysis of reproductive data of individual animals were performed personally. In dairy herds, the results of previous examinations of milk, abortion products, and serum of aborted animals with at least one C. burnetii positive sample were used to indicate the incidence of Q fever. Herds that were C. burnetii negative were recognized as Q fever-unaffected herds. Q fever-affected (n=60) and unaffected (n=58) herds were selected randomly, covering the entire territory of Latvia. We used monitoring data obtained in the Agricultural Data Center to determine the herds' characteristic indicators (number of animals, milk yield, milk content indicators in different groups of animals, number of milking days, age of first artificial insemination and first calving in heifers, service and hard standing period and number of artificial insemination times per pregnancy). In order to identify risk factors possibly contributing to the spread of Q fever related to husbandry practices and the frequency of occurrence of health indicators related to reproduction, a survey of farm owners/service veterinarians was conducted in Q fever-affected (n=36) and unaffected (n=22) herds. In order to detect the C. burnetii serological response in serum and presence in milk, 140 individual animal samples were initially collected in 15 dairy cow herds to determine the nature, dynamics, and relationship of the anamnesis of reproduction problems of Q fever. In order to assess the nature and dynamics of the spread, samples were collected twice with an interval of 7-13 months, re-sampling from 115 animals. For further evaluation of reproductive performance and productivity in animals after abortion, individual data of aborted animals (n=297) were compared both with each other and against herd averages. Summarizing the indicators characteristic of herds affected by Q fever, the following were significantly different: higher milk yield, higher fat, protein, and lactose content in standard lactation, and higher number of animals in all animal groups. On the other hand, in herds unaffected by Q fever, a lower number of artificial insemination times per pregnancy was found to be significantly better. In order to identify the possible risk factors contributing to the spread of Q fever, the following were found to be important: a large number of dairy cows in the herd, a high territorial density of cattle, a separate calving area, artificial ventilation in the shelter, the type of untied keeping and the change of staff clothing or the use of outerwear. It was also found that ticks observed on dairy cows and pasture use are not associated with an increased incidence of Q fever. Treatment of cattle hoofs, the openness of the farm to visitors (seminars, tours), and the number of employees on the farm were other significant possible risk factors for the spread of the disease. When evaluating the incidence of twin pregnancies, dystocia, stillborn offspring, and abortions during the last year, it was significantly higher in Q fever-affected herds. In the affected herds, when investigating the causes of abortions, Q fever was the second most frequent laboratory-confirmed diagnosis. A significantly higher incidence of acute postpartum metritis was also found in affected herds. However, ironically, in Q fever-affected herds, animals were most often culled due to leg problems, with reproduction and udder problems ranking second and third, respectively. An assessment of C. burnetii prevalence at the herd level found that it continued and even increased without containment measures. At the level of individual animals, in C. burnetii positive animals, we found the preservation of the existing immune response and its presence in milk, the occurrence of several types of immune response in repeated examination in initially seronegative animals, and a change in the type of immune response to another/opposite. We found new cases of infection in initially seronegative pregnant heifers. When evaluating the relationship between the immune response and the presence of C. burnetii with reproduction problems in the anamnesis of the animals, we found that the C. burnetii phase I antigen and the typical immune response were found significantly more often in animals with reproduction problems in anamnesis compared to the control group. When collecting data on the further use and potential of animals after abortion, we found high rates of culling of animals. However, in the event of a new pregnancy after abortion, reproduction rates did not significantly deteriorate. Comparing the subsequent productivity of aborted animals, we found significantly lower productivity indicators. Six conclusions and four practical recommendations have been formulated at the end of the doctoral thesis. There are 113 pages, 16 tables, 42 figures and attached appendix. The bibliograpfy contains 206 references.