The objective of this study was to know the herd and animal level prevalence of Q fever in domestic ruminants in some selected districts in Bangladesh. Randomly collected 111 bulk milk and 94 sera samples of cattle, sheep, and goats were tested by indirect ELISA (iELISA). DNA extracted from 23 aborted fetal membranes was analyzed by real time (rt) PCR. The positive cut-off value of iELISA in bulk milk and individual animal sera was ≥30% and ≥40%, respectively. The overall herd level prevalence of Q fever in dairy cattle was 15.6%. The prevalence of Q fever in dairy cattle was significantly higher in Sirajganj in comparison to Satkhira District (
Q (for Query) fever is a ubiquitous zoonosis caused by an obligate intracellular bacterium
In humans, Q fever is mostly asymptomatic but may be responsible for acute or chronic disease conditions such as influenza-like illness, pneumonia, hepatitis, meningoencephalitis, myocarditis, endocarditis, and chronic fatigue syndrome in persistently infected patients and may contribute to abortion and stillbirth in pregnant women [
Diagnosis of Q fever in animals is based on detection of bacteria, bacterial DNA, or antibodies [
Although Q fever is present worldwide, its status in animals, humans, arthropods, birds, wild animals, and other reservoirs in Bangladesh is not known except one report on serological evidence in cattle and goats [
This study used milk samples from two previous studies, which were undertaken in the Department of Medicine, BAU, Mymensingh 2202. In one study, 399 randomly collected bulk milk samples were examined for somatic cell count from where 94 samples were used in this study. The history of reproductive failure in the selected dairy herds was not known. In another study, 17 milk ring test positive samples were sent to Belgium for isolation of
Serum samples were collected from a serum bank in the Department of Medicine, BAU, Mymensingh. Those samples were randomly collected to study brucellosis in cattle, sheep, and goats in different districts of Bangladesh in 2007 and 2008 [
Twenty-three DNA samples (5 from cattle, 10 from goats, and 8 from sheep) extracted from aborted fetal membranes for the detection of
Animal level data on age, breed, sex, and pregnancy status and herd level data on herd size, herd composition, and location of the herd were collected from available database of serum samples.
For milk samples, the location of the farm and number of lactating cows in herd were collected from the bovine mastitis database.
The milk and sera samples were prepared according to the instructions of commercial kit. In brief, 10 milliliters of milk from each selected herd was collected for testing antibody against
All reagents were taken into 18–26°C before use. The reagents were mixed by shaking gently. All samples were tested in duplicate and the optical densities (OD) of the samples were averaged and corrected by subtracting the OD of the negative control. Both milk and serum based tests were performed using the commercial CHEKIT Q Fever Antibody ELISA Test Kit (IDEXX, Liebefeld-Bern, Switzerland) based on
The real time (rt) PCR assay was performed using a 7500 rt PCR System (Applied Biosystems). Samples were considered positive with a cycle threshold (Ct) < 40 [
The association of herd and animal level factors with Q fever prevalence was analyzed by
The serum samples were collected from 40 herds where there was history of abortion in any of the three domestic ruminant species in the last year. The herd size varied from 1 to 20 with a median of 3 animals. Thirteen herds consisted of only cattle, 13 of only goats, 8 of both cattle and goats, and 6 of only sheep. In 55.0% (22/40) herd’s aborted materials were disposed by burial but in the rest of the herds the materials were thrown away in the field or in nearby water bodies. About 35% (14/40) farmers were found to keep sheep (7.5%) or goats (27.5%) inside their house at night.
The age of cattle varied from 4 months to 12 years with a median of 6 years. The range and median age of goats and sheep, respectively, were 2.5 months to 4 years and 2 years, 1 month to 4 years and 8 months. Among cattle 82.0% were female and indigenous and all of the sheep were indigenous and 74.2% of them were female but 80.0% and 94.0% goats were female and Black Bengal breed type, respectively. The range of positive S/P value in cattle herds was 41.4 to 123.0.
A summary of ELISA test results on the presence of
Summary of iELISA tests results on the presence of
Test result | Number of herds/flocks | Apparent prevalence | 95% CI | Range of S/P values (%) | Mean S/P values (%) |
---|---|---|---|---|---|
Positive (S/P ≥ 30%) | 17 (cattle) | 15.6% | 9.4–23.8 | 41.4–123.0 | 81.3 |
Negative (S/P < 30%) | 92 | 84.4% | 76.2–90.6 | 0–25.9 | 5.6 |
Positive (S/P ≥ 30%) | 2 (goats) |
421.6 and 424.2 |
Distribution of herd level prevalence of Q fever based on iELISA using bulk milk.
Variable | Tested | Positive (>40%) | Prevalence | 95% CI |
|
---|---|---|---|---|---|
District | <0.01 | ||||
Satkhira | 28 | 2 | 7.1 | 0.9–23.5 | |
Chittagong | 55 | 6 | 10.9 | 4.1–22.2 | |
Sirajganj | 26 | 9 | 34.6 | 17.2–55.6 | |
Number of lactating cows | 1 | ||||
>5 | 22 | 3 | 13.6 | 2.9–34.9 | |
1 to 5 | 87 | 14 | 16.1 | 9.1–15.5 | |
Breed composition | 0.29 | ||||
Sahiwal cross | 18 | 2 | 11.1 | 1.4–34.7 | |
Friesian cross | 73 | 10 | 13.7 | 6.8–23.8 | |
Both | 18 | 5 | 27.8 | 9.7–53.5 |
The other two bulk milk samples were collected from two government goat farms in Savar, Dhaka, and Rajshahi Districts; CI: Confidence Interval.
The summary of ELISA test results on the presence of
Summary of iELISA tests results on the presence of
Test result | Number | Prevalence (%) | 95% Confidence Interval | Range of S/P values (%) | Mean S/P values (%) |
---|---|---|---|---|---|
Positive (S/P ≥ 40%) | 4 | 5.06 | 1.63–13.14 | 42.70–49.80 | 45.35 |
Suspect (30% ≤ S/P < 40%) | 3 | 3.79 | 0.98–11.45 | 30.10–34.50 | 32.40 |
Negative (S/P < 30%) | 72 | 91.13 | 82.04–96.06 | 0–29.80 | 5.13 |
The distribution of seroprevalence of Q fever in domestic ruminants.
Variable | Tested | Positive | Prevalence (95% CI) |
|
---|---|---|---|---|
Species | 0.55 | |||
Cattle | 28 | 1 | 3.57 (0.18–20.24) | |
Sheep | 21 | 2 | 9.52 (1.67–31.83) | |
Goats | 30 | 1 | 3.33 (0.17–19.05) | |
Sex | 1.00 | |||
Male | 15 | 1 | 6.67 (0.34–33.96) | |
Female | 64 | 3 | 4.69 (1.22–13.96) | |
Pregnancy | 0.63 | |||
No | 38 | 1 | 2.63 (0.14–15.43) | |
Yes | 26 | 2 | 7.69 (1.34–26.59) | |
Male | 15 | 1 | 6.67 (0.34–33.96) | |
District | 1.00 | |||
Sherpur | 25 | 1 | 4.0 (0.21–22.32) | |
Cattle | 16 | 0 | 0 (0–24.07 |
|
Sheep | 0 | 0 | ||
Goats | 9 | 1 | 11.11 (0.58–49.33) | |
Mymensingh | 54 | 3 | 5.56 (1.44–16.34) | |
Cattle | 12 | 1 | 8.33 (0.44–40.25) | |
Sheep | 21 | 2 | 9.52 (1.67–31.83) | |
Goats | 21 | 0 | 0 (0–19.24 |
CI: Confidence Interval;
The demographic characteristics of the four Q fever seropositive domestic ruminants are shown in Table
Characteristics of the four Q fever seropositive domestic ruminants.
Farmer ID | Area | Species | Age | Breed | Sex | Body weight | S/P value (%) |
---|---|---|---|---|---|---|---|
Fa 50 | Sirta, Mymensingh Sadar | Cattle | 6 years | Indigenous | Female | 200 | 42.7 |
Fa 268 | Noyabil, Sherpur | Goat | 1 year | Black Bengal | Female | 6 | 49.8 |
Fa 543 | Buror Chor, Mymensingh Sadar | Sheep | 10 months | Indigenous | Male entire | 12 | 43.4 |
Fa 548 | Buror Chor, Mymensingh Sadar | Sheep | 1.5 years | Indigenous | Female | 18 | 45.5 |
In this study the herd level prevalence of Q fever in cattle based on bulk milk and animal level seroprevalence of Q fever in cattle, goats, and sheep were estimated by using indirect ELISA test. The overall prevalence of Q fever in bulk cow milk was 15.6% indicating that Q fever is an existing disease in dairy cattle population in Bangladesh. The herds under study were originated from major milk pockets of Bangladesh like Sirajganj, Chittagong, and Satkhira Districts (Figure
We have tested only bulk milk, which does not allow identification of individual cows infected with Q fever. However, it is very useful for screening herds under disease surveillance system. A large epidemiologic study including representative dairy herds of Bangladesh will help to reveal the herd level status of this disease in Bangladesh. Out of three study areas, significantly higher prevalence of Q fever was found in dairy herds of Sirajganj than Satkhira District. The cattle management system in Sirajganj area slightly varies from that of other parts of Bangladesh. In the dry season, the cattle graze freely and remain in the pasture (“Bathan”) for almost six months (December to May). As a result, a lot of intermingling among cattle of different owners occurs during that period. Intermixing of cattle from different owners may facilitate the transmission of infection in dairy cattle herds of this area. In some herd, presence of sheep is also noticed in that period. Environment conditions in dry season could play a role in the survival of the bacteria and facilitate the transmission between animals as well. Similarly, higher prevalence of Q fever in loose housing system was also reported by Paul et al. [
We have observed relatively higher seroprevalence of Q fever in sheep than cattle and goats. Similar observations were also reported by other authors [
In our study, serum samples of the animals were originated from herds where there was history of abortion in previous year. Out of four seropositive cases two were in sheep indicating that Q fever might have some role in sheep abortion. Our rt PCR result also supports this hypothesis. An rt PCR Q fever positive result in the placenta means a contact with the bacteria. To confirm an abortion caused by
It is revealed from this study that Q fever is present in all of the three important domestic ruminant species in Bangladesh. It may have some role in sheep abortion as the seroprevalence is relatively higher and one sheep placenta is rt PCR positive.
The authors declare that they have no competing interests.
This research work was funded by the Seed Bull Production Project (SPGR fund) in the Department of Animal Breeding and Genetics, BAU, and the NST Authority. The authors are grateful to Professor Dr. Md. Taohidul Islam, Department of Medicine, BAU, Mymensingh, for providing bulk milk samples and to Dr. David Fretin of Veterinary Agrochemical Research Centre, Brussels, Belgium, for the support on real time PCR.