Infection, Genetics and Evolution 28 (2014) 150–150
Contents lists available at ScienceDirect
Infection, Genetics and Evolution journal homepage: www.elsevier.com/locate/meegid
Letter To the Editor Coxiella burnetii and reproductive disorders in cattle
Sir, In their recent publication in Infection, Genetics and Evolution, Das et al. (2014) study Coxiella burnetii isolates from the blood of cattle, buffaloes and bitches suffering from a heterogeneous group of reproductive disorders. In the introduction to the study, the authors state that the infection is associated with abortions, especially in sheep and goats and also in cattle, usually along with infertility and other reproductive problems. The authors use the study by To et al. (1995) and my recent review (Agerholm, 2013) as references to the last part of the statement. It is correct that C. burnetii may be associated with abortion in ruminants, but there is no solid evidence for an association with infertility or other reproductive disorders in cattle. The authors erroneously refer to my recent review (Agerholm, 2013) where I state exactly the opposite, namely that evidence has not been provided for a causal association between C. burnetii and other bovine reproductive disorders than abortion. The other reference used by the authors to support their statement (To et al., 1995) report prevalences of C. burnetii isolation from milk and genital tract swabs of groups of cattle with (insufficiently defined) reproductive disorders. It is well known that C. burnetii is excreted through milk and uterine fluids in cattle (see my recent review for further details and references) and not surprisingly, To found the organism in these materials. But without inclusion of appropriate age-matching controls, clear case definitions and supportive statistics such prevalence studies remain inconclusive regarding the association between reproductive disorders and a ubiquitously occurring pathogen like C. burnetii even though they are referred to repeatedly. The key objective of the study by Das et al. was to isolate C. burnetii from trans-PCR positive samples originating from animals having a history of reproductive disorders. Although Das et al. have a molecular focus, they still study clinical samples. To be able to
http://dx.doi.org/10.1016/j.meegid.2014.09.023 1567-1348/Ó 2014 Elsevier B.V. All rights reserved.
repeat their study, compare with other studies and make full use of their results, one need detailed knowledge on their materials. Unfortunately the authors use poorly defined case definitions and by not presenting details such as number of cases within each disease category, they unfortunately make their results less useful. Clear case definitions and transparent data is a must in research. It is interesting that the authors isolated C. burnetii from blood samples. Most animal studies have used milk or genital tract fluids as these are well known to harbor the organism. The presence of the organism in blood shows that cattle and buffaloes may develop coxiellaemia, which is suspected but poorly investigated. Presentation of details on the clinical appearance of these animals (at least which disease category they belonged to) would have made the finding interesting for a broader group of researchers, although I recognize that clinical medicine is not covered by the main scope of the journal. References Agerholm, J.S., 2013. Coxiella burnetii associated reproductive disorders in domestic animals – a critical review. Acta Vet. Scand. 55, 13. Das, D.P., Malik, S.V., Rawool, D.B., Das, S., Shoukat, S., Gandham, R.K., Saxena, S., Singh, R., Doijad, S.P., Barbuddhe, S.B., 2014. Isolation of Coxiella burnetii from bovines with history of reproductive disorders in India and phylogenetic inference based on the partial sequencing of IS1111 element. Infect. Genet. Evol. 22, 67–71. To, H., Htwe, K.K., Yamasaki, N., Zhang, G.Q., Ogawa, M., Yamaguchi, T., Fukushi, H., Hirai, K., 1995. Isolation of Coxiella burnetii from dairy cattle and ticks, and some characteristics of the isolates in Japan. Microbiol. Immunol. 39, 663–671.
Jørgen S. Agerholm Section for Veterinary Reproduction and Obstetrics, Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 68, DK-1870 Frederiksberg C, Denmark Tel.: +45 35332981. E-mail address: [email protected] Available online 29 September 2014
Contents lists available at ScienceDirect
Infection, Genetics and Evolution journal homepage: www.elsevier.com/locate/meegid
Letter To the Editor Coxiella burnetii and reproductive disorders in cattle
Sir, In their recent publication in Infection, Genetics and Evolution, Das et al. (2014) study Coxiella burnetii isolates from the blood of cattle, buffaloes and bitches suffering from a heterogeneous group of reproductive disorders. In the introduction to the study, the authors state that the infection is associated with abortions, especially in sheep and goats and also in cattle, usually along with infertility and other reproductive problems. The authors use the study by To et al. (1995) and my recent review (Agerholm, 2013) as references to the last part of the statement. It is correct that C. burnetii may be associated with abortion in ruminants, but there is no solid evidence for an association with infertility or other reproductive disorders in cattle. The authors erroneously refer to my recent review (Agerholm, 2013) where I state exactly the opposite, namely that evidence has not been provided for a causal association between C. burnetii and other bovine reproductive disorders than abortion. The other reference used by the authors to support their statement (To et al., 1995) report prevalences of C. burnetii isolation from milk and genital tract swabs of groups of cattle with (insufficiently defined) reproductive disorders. It is well known that C. burnetii is excreted through milk and uterine fluids in cattle (see my recent review for further details and references) and not surprisingly, To found the organism in these materials. But without inclusion of appropriate age-matching controls, clear case definitions and supportive statistics such prevalence studies remain inconclusive regarding the association between reproductive disorders and a ubiquitously occurring pathogen like C. burnetii even though they are referred to repeatedly. The key objective of the study by Das et al. was to isolate C. burnetii from trans-PCR positive samples originating from animals having a history of reproductive disorders. Although Das et al. have a molecular focus, they still study clinical samples. To be able to
http://dx.doi.org/10.1016/j.meegid.2014.09.023 1567-1348/Ó 2014 Elsevier B.V. All rights reserved.
repeat their study, compare with other studies and make full use of their results, one need detailed knowledge on their materials. Unfortunately the authors use poorly defined case definitions and by not presenting details such as number of cases within each disease category, they unfortunately make their results less useful. Clear case definitions and transparent data is a must in research. It is interesting that the authors isolated C. burnetii from blood samples. Most animal studies have used milk or genital tract fluids as these are well known to harbor the organism. The presence of the organism in blood shows that cattle and buffaloes may develop coxiellaemia, which is suspected but poorly investigated. Presentation of details on the clinical appearance of these animals (at least which disease category they belonged to) would have made the finding interesting for a broader group of researchers, although I recognize that clinical medicine is not covered by the main scope of the journal. References Agerholm, J.S., 2013. Coxiella burnetii associated reproductive disorders in domestic animals – a critical review. Acta Vet. Scand. 55, 13. Das, D.P., Malik, S.V., Rawool, D.B., Das, S., Shoukat, S., Gandham, R.K., Saxena, S., Singh, R., Doijad, S.P., Barbuddhe, S.B., 2014. Isolation of Coxiella burnetii from bovines with history of reproductive disorders in India and phylogenetic inference based on the partial sequencing of IS1111 element. Infect. Genet. Evol. 22, 67–71. To, H., Htwe, K.K., Yamasaki, N., Zhang, G.Q., Ogawa, M., Yamaguchi, T., Fukushi, H., Hirai, K., 1995. Isolation of Coxiella burnetii from dairy cattle and ticks, and some characteristics of the isolates in Japan. Microbiol. Immunol. 39, 663–671.
Jørgen S. Agerholm Section for Veterinary Reproduction and Obstetrics, Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 68, DK-1870 Frederiksberg C, Denmark Tel.: +45 35332981. E-mail address: [email protected] Available online 29 September 2014
