Infectious Abortions in Small Ruminants: Challenges for Diagnosis and Public Health

Case Report

In April 2017, a family farm in central Kosovo consisting of goats, sheep, and cows reported an abortion rate of 70% in goats and sheep in the last trimester. The abortions were associated with vaginal discharge, weakness, lameness, high temperature, and retention of the placenta in almost all animals and weak newborns that died after 24 h. The aim of the study was to identify the cause of the abortion outbreak by testing the animals for the most commonly reported abortion pathogens in the region. For this purpose, blood samples were collected from all the animals in the household, including 146 goats, 12 sheep, and 12 cows, in compliance with animal welfare measures.

Considering that Brucella spp. is a common abortion pathogen, all samples were first tested for the presence of Brucella spp. antibodies using the Rose Bengal method (OIE, 2018), which resulted in 2 (1%) positive goats; all sheep and cows tested negative. Consequently, all goats were tested for Chlamydophila abortus antibodies using the ID Screen C. abortus Indirect Multi-species enzyme-linked immunosorbent assay (ELISA) kit (ID.vet, France), resulting in 59 (40%) goats positive and 16 suspicious for C. abortus. Owing to the disproportion between the results and the abortion rate, after 2 weeks all sera were tested for Coxiella burnetii using a commercial ELISA Antibody Test Kit (Idexx, France); 96 (66%) were positive and 12 were suspicious for C. burnetii (Table 1).

In early 2018, the same goat herd exhibited 75% abortion rate in the following winter pregnancy. Blood and milk samples from aborting goats were collected to identify the aborting pathogen and to assess the public health risk posed by milk and animal handling. Seventy-three sera from 123 goats were analyzed for C. burnetii and C. abortus using the same commercial ELISA kits. In addition, 37 corresponding sera were analyzed for Brucella spp. using the Rose Bengal method and for Toxoplasma gondii using ID Screen Toxoplasmosis Indirect Multi-species (ID.vet, France). To assess the safety of milk, 51 milk samples from 73 goats were tested for C. burnetii and Brucella spp. by molecular analysis. Initially, DNA was extracted from 16 individual samples to obtain preliminary results on the presence of bacterial pathogens in the herd. According to the preliminary polymerase chain reaction (PCR) and ELISA results, the other 35 milk samples were pooled into 8 pools. DNA was extracted using DNeasy Blood and Tissue Kit (Qiagen, Germany) after a preprocessing step was performed to concentrate the bacteria (Gao et al. 2007). For the detection of C. burnetii the primer and probe sequences targeting the IS1111 gene of C. burnetii were used, as previously published by Schneeberger et al. (2010), whereas for the detection of Brucella spp. the real-time PCR targeting the bscp31 gene was applied according to the instructions of LightMix Kit Brucella Genus (TIB Molbiol, Germany). Of 73 sera tested, 40 (55%) samples were positive and 7 suspicious for C. burnetii and 26 positive (36%) and 1 suspicious sample for C. abortus. Mixed infections with C. burnetii and C. abortus resulted in 22 (30%) cases out of a total of 73 sera. All 37 corresponding sera were negative for Brucella spp. and 8 samples (22%) were positive for T. gondii. Of the total 37 sera tested for 4 pathogens, 4 cases resulted in mixed infections with 3 pathogens, including 3 cases with C. burnetii, C. abortus, and T. gondii, and 1 case with C. burnetii, C. abortus, and Brucella spp. Three milk samples from 16 individual samples and another 3 pools from 8 milk pool samples were positive for C. burnetii by real-time PCR. All milk samples were negative for Brucella spp. (Table 1).

After the first abortion outbreak in goats, human blood sera from 10 family members living on the farm were tested for brucellosis by Wright's test and for IgG antibodies to C. burnetii phases 1 and 2 and IgM antibodies to phase 2 by ELISA (NovaTec, Immunodiagnostica, Germany). Three serum samples from 10 household family members, including 2 men and 1 woman, aged between 30 and 65 years, were positive for C. burnetii IgG phase 1 antibodies and 1 was positive for brucellosis, as shown in Table 1.

Discussion

The results from two outbreak scenarios showed C. burnetii as the most likely causative agent of the abortions, as the abortion rate in both years matched the prevalence found serologically. Exposure of the pathogen on the farm could be related to the breeding environment with different animal species such as sheep, goats, cattle, and dogs. Positive milk samples found by real-time PCR suggest that C. burnetii is shed in milk and could be acquired through milk or unpasteurized milk products. The clinical history of three family members positive for C. burnetii included bronchitis in the older member and pain in the back, hands, and arms, sweating and headache in the other two. Positive results for C. burnetii phase 1 IgG antibodies suggest that chronic Q fever was most likely related to animal handling, because of close contact with animals or consumption of raw milk. There is always a risk of aerosol spread of C. burnetii into the environment, as reported in 2005 in the Argentinian police unit in Kosovo (Faas et al. 2007). Vaccination of animals is the most important measure to eradicate and control C. burnetii, as reported in The Netherlands (Hogerwerf et al. 2011). With regard to C. abortus, which was also serologically detected in this study, after an abortion caused by C. abortus, ewes are considered immune and will not abort again (Essig and Longbottom 2015); therefore, C. abortus has not been identified as a cause of abortion outbreaks. T. gondii was found with a low prevalence and should not be considered as the main abortive pathogen. Brucella spp. was also ruled out as an abortive pathogen in both outbreaks. Viral diseases such as caprine herpesviruses and Mycoplasma spp. should be considered in future abortions.

In conclusion, C. burnetii was the most likely cause of abortions in both outbreak scenarios and was reported for the first time in Kosovo. Active surveillance of C. burnetii needs to be initiated and the regulation for control needs to be developed.