Ahead of Print -Accuracy of Herdsmen Reporting versus Serologic Testing for Estimating Foot-and-Mouth Disease Prevalence - Volume 20, Number 12—December 2014 - Emerging Infectious Disease journal - CDC
Volume 20, Number 12—December 2014
Accuracy of Herdsmen Reporting versus Serologic Testing for Estimating Foot-and-Mouth Disease Prevalence
Owner-, farmer-, or herdsman-reported disease prevalence is widely used in veterinary epidemiologic studies (1–6), especially for diseases that produce visible external lesions (e.g., ovine myiasis, foot-and-mouth disease [FMD]) (1,5) or characteristic clinical signs (e.g., scrapie) (7). For such interview- or questionnaire-based reporting, a common criticism is lack of external validation because questionnaires, like other measuring devices, need to be calibrated. External validation is usually approached by comparing questionnaire data with data measured by other methods such as visual inspection (8–10), photographs (11), selection of clinical signs (2,4), laboratory test results (12), or other (4,13). These approaches, however, are difficult to use in poorer countries and pastoral populations, where there are limited resources and no comparison data. We estimated sensitivity and specificity of herdsman-reported FMD prevalence in the Adamawa plateau, Cameroon, and compared herdsmen’s estimates with serologic test results.
FMD is a highly contagious viral disease of even-toed ungulates, caused by FMD viruses in the family Picornaviridae. Globally, FMD is a major disease of livestock because it leads to production losses and restrictions on trade with FMD-free countries (14). Clinical signs in cattle are distinct: vesicles on the tongue, gums, coronary band, and occasionally, udder. Animals salivate and are febrile, lame, and inappetant. Ruptured vesicles leave ulcers with characteristic underrun epithelial tissue at the edges (15).
To assess herdsmen’s ability to correctly identify FMD and to compare the sensitivity and specificity of herdsman reporting with that of serologic testing, we conducted a cross-sectional study of FMD on the Adamawa plateau, the major cattle-rearing area of Cameroon. We used a structured questionnaire, administered by interview, to determine whether herdsmen had seen FMD in their herds in the previous 1 and 2 years (5,16). Their ability to correctly identify FMD was also assessed by showing them color photographs of typical lesions. To estimate the sensitivity and specificity of the various estimates, we used Bayesian latent class models. These estimates were arrived at by restricting the age of cattle analyzed by virus neutralization (VN) testing to <2 years and by adopting evidence that nonstructural protein (NSP) antibody titers fall more rapidly (over ≈1 year) than VN antibodies (17,18). The study was conducted in accordance with the Cameroonian Ministry of Research guidelines and with approval from the University of Liverpool ethics committee in 1999.
Dr Morgan is a veterinarian at the University of Liverpool. His research interests include racehorse injuries, exotic and endemic diseases of farmed animals, aquatic animal health, molecular epidemiology of rotavirus, and use of machine learning in epidemiology.
We thank all the herdsmen, heads of veterinary centers, and regional Ministère de l'Elevage, des Pêches et des Industries Animales delegates who made this study possible.
This work was supported by the Wellcome Trust (WT 053480). B.M. de C.B. held a Wellcome Trust Training Fellowship in Tropical Epidemiology but reports no conflict of interest. Cattle were sampled by a veterinary surgeon with the cattle owners’ consent.
- French NP, Wall R, Cripps PJ, Morgan KL. Prevalence, regional distribution and control of blowfly strike in England and Wales. Vet Rec.1992;131:337–42.
- Cetinkaya B, Erdogan HM, Morgan KL. Prevalence, incidence and geographical distribution of Johne’s disease in cattle in England and the Welsh borders. Vet Rec. 1998;143:265–9.
- Erdogan HM, Cetinkaya B, Green LE, Green LE, Cripps PJ, Morgan KL. Prevalence, incidence, signs and treatment of clinical listeriosis in dairy cattle in England. Vet Rec. 2001;149:289–93 .
- Bronsvoort BM, Tanya VN, Kitching RP, Nfon C, Hamman SM, Morgan KL. Foot and mouth disease and livestock husbandry practices in the Adamawa Province of Cameroon. Trop Anim Health Prod. 2003;35:491–507.
- Hermans PG, Morgan KL. Prevalence and associated risk factors of necrotic enteritis on broiler farms in the United Kingdom; a cross-sectional survey. Avian Pathol. 2007;36:43–51.
- Inness CM, Morgan KL. Polo pony injuries: player-owner reported risk, perception, mitigation and risk factors. Equine Vet J. 2014 [cited 2014 Sep 29]. Epub ahead of print. http://onlinelibrary.wiley.com/doi/10.1111/evj.12298
- Healy AM, Morgan KL, Hannon D, Collins JD, Weavers E, Doherty ML. Postal questionnaire survey of scrapie in sheep flocks in Ireland. Vet Rec.2004;155:493–4.
- Nespeca R, Vaillancourt JP, Morrow WE. Validation of a poultry biosecurity survey. Prev Vet Med. 1997;31:73–86.
- Vanderhaeghe C, Dewulf J, Ribbens S, de Kruif A, Maes D. A cross-sectional study to collect risk factors associated with stillbirths in pig herds. Anim Reprod Sci. 2010;118:62–8.
- Knight-Jones TJ, Gibbens J, Wooldridge M, Stärk KD. Assessment of farm-level biosecurity measures after an outbreak of avian influenza in the United Kingdom. Transbound Emerg Dis. 2011;58:69–75.
- Kaler J, Green LE. Naming and recognition of six foot lesions of sheep using written and pictorial information: a study of 809 English sheep farmers.Prev Vet Med. 2008;83:52–64.
- Catley A, Chibunda RT, Ranga E, Makungu S, Magayane FT, Magoma G, Participatory diagnosis of a heat-intolerance syndrome in cattle in Tanzania and association with foot-and-mouth disease. Prev Vet Med. 2004;65:17–30.
- Doherr MG, Carpenter TE, Wilson WD, Gardner IA. Application and evaluation of a mailed questionnaire for an epidemiologic study ofCorynebacterium pseudotuberculosis infection in horses. Prev Vet Med. 1998;35:241–53.
- Perry B, Sones K. Science for development. Poverty reduction through animal health. Science. 2007;315:333–4.
- Kitching RP. Clinical variation in foot and mouth disease: cattle. Rev Sci Tech. 2002;21:499–504 .
- de C. Bronsvoort BM. Nfon C, Hamman SM, Tanya VN, Kitching RP, Morgan KL. Risk factors for herdsman-reported foot-and-mouth disease in the Adamawa Province of Cameroon. Prev Vet Med. 2004;66:127–39.
- Silberstein E, Kaplan G, Taboga O, Duffy S, Palma E. Foot-and-mouth disease virus-infected but not vaccinated cattle develop antibodies against recombinant 3AB1 nonstructural protein. Arch Virol. 1997;142:795–805.
- Brocchi E, Bergmann IE, Dekker A, Paton DJ, Sammin DJ, Greiner M, Comparative evaluation of six ELISAs for the detection of antibodies to the non-structural proteins of foot-and-mouth disease virus. Vaccine. 2006;24:6966–79.
- Lee JA, More SJ, Cotiwan BS. Problems translating a questionnaire in a cross-cultural setting. Prev Vet Med. 1999;41:187–94.
- Kitching RP, Barnett PV, Donaldson AI, Mackay D. Foot-and-mouth disease. In: Linnane S, editor. Manual of standards for diagnostic tests and vaccines. Paris: Office International des Epizooties; 2000. p. 77–92.
- de C. Bronsvoort BM. Anderson J, Corteyn A, Hamblin P, Kitching RP, Nfon C, et al. Geographical and age-stratified distributions of foot-and-mouth disease virus-seropositive and probang-positive cattle herds in the Adamawa province of Cameroon. Vet Rec. 2006;159:299–308.
- Malirat V, Neitzert E, Bergmann IE, Maradei E, Beck E. Detection of cattle exposed to foot-and-mouth disease virus by means of an indirect ELISA test using bioengineered nonstructural polyprotein 3ABC. Vet Q. 1998;20(Suppl 2):S24–6.
- Bronsvoort BM, Toft N, Bergmann IE, Sørensen KJ, Anderson J, Malirat V, Evaluation of three 3ABC ELISAs for foot-and-mouth disease non-structural antibodies using latent class analysis. BMC Vet Res. 2006;2:30.
- Sørensen KJ, de Stricker K, Dyrting KC, Grazioli S, Haas B. Differentiation of foot-and-mouth disease virus infected animals from vaccinated animals using a blocking ELISA based on baculovirus expressed FMDV 3ABC antigen and a 3ABC monoclonal antibody. Arch Virol. 2005;150:805–14.
- Bronsvoort BMC, Sørensen KJ, Anderson J, Corteyn A, Tanya VN, Kitching RP, A comparison of two 3ABC enzyme-linked immunosorbent assays in a cattle population with endemic, multiple-serotype foot-and-mouth disease. J Clin Microbiol. 2004;42:2108–14.
- Hui SL, Walter S. Estimating the error rates of diagnostic tests. Biometrics. 1980;36:167–71.
- Enøe C, Georgiadis MP, Johnson WO. Estimation of sensitivity and specificity of diagnostic tests and disease prevalence when the true disease state is unknown. Prev Vet Med. 2000;45:61–81.
- Johnson WO, Gastwirth JL, Pearson LM. Screening without a gold standard: the Hui–Walter paradigm revisited. Am J Epidemiol. 2001;153:921–4.
- Toft N, Jørgensen E, Højsgaard S. Diagnosing diagnostic tests: evaluating the assumptions underlying the estimation of sensitivity and specificity in the absence of a gold standard. Prev Vet Med. 2005;68:19–33.
- Gelman A, Rubin DB. Inference from iterative simulation using multiple sequences. Stat Sci. 1992;7:457–72.
- Fu Y, Cao Y, Sun P, Bao H, Bai X, Li P, Development of a dot immunoblot method for differentiation of animals infected with foot-and-mouth disease virus from vaccinated animals using non-structural proteins expressed prokaryotically. J Virol Methods. 2011;171:234–40.
- Mackay DKJ. Forsyth MA, Davies PR, Berlinzani A, Belsham GJ, Flint M, et al. Differentiating infection from vaccination in foot-and-mouth disease using a panel of recombinant, non-structural proteins in ELISA. Vaccine. 1998;16:446–59.
- Lubroth J, Brown F. Identification of native foot-and-mouth disease virus non-structural protein 2C as a serological indicator to differentiate infected from vaccinated livestock. Res Vet Sci. 1995;59:70–8.
- van Smeden M, Naaktgeboren CA, Reitsma JB, Moons KG, de Groot JA. Latent class models in diagnostic studies when there is no reference standard—a systematic review. Am J Epidemiol. 2014;179:423–31.
- Torrance-Rynard VL, Walter SD. Effects of dependent errors in the assessment of diagnostic test performance. Stat Med. 1997;16:2157–75.
- Spencer BD. When do latent class models overstate accuracy for diagnostic and other classifiers in the absence of a gold standard? Biometrics.2012;68:559–66.
- Frantz C. Are the Mbororo’en boring and are the Fulani finished? In: Eguchi PK, Azarya V, editors. Unity and diversity. Senri ethnological studies 35. Osaka (Japan): National Museum of Ethnography; 1993. p. 11–34.
- Deregowski JB. What about pictures? Behav Brain Sci. 1993;16:757–61.
Suggested citation for this article: Morgan KL, Handel IG, Tanya VN, Hamman SM, Nfon C, Bergman IE, et al. Accuracy of herdsmen reporting versus serologic testing for estimating foot-and-mouth disease prevalence. Emerg Infect Dis [Internet]. 2014 Dec [date cited].http://dx.doi.org/10.3201/eid2012.140931
1Current affiliation: Canadian Food Inspection Agency, Winnipeg, Manitoba, Canada.