title: Temporal fluctuations in the sero-prevalence of Taenia solium cysticercosis in pigs in Mbeya Region, Tanzania.
abstract: BACKGROUND
  Porcine cysticercosis is an emerging agricultural problem in sub-Saharan Africa. This has been documented primarily through cross-sectional studies, however detailed knowledge of the transmission dynamics of this disease in sub-Saharan Africa is lacking. This study aims to describe seasonal variations in sero-prevalence of antigen ELISA positive porcine cysticercosis in an endemic area.
  
  
  METHODS
  A longitudinal study composed of three cross-sectional surveys was carried out in Mbeya Region, Tanzania; the first two six months apart (March/April 2012 and October/November 2012) and the last eight months later (July/August 2013). Venous blood was collected from pigs in 22 villages and analysed using Ag-ELISA.
  
  
  RESULTS
  In each survey between 800-1000 serum samples were collected. The first survey revealed a cysticercosis sero-prevalence of 15% (n = 822, 95% CI: 13-18%). The sero-prevalence had significantly increased to 24% (p < 0.001, χ2-test, n = 812, 95% CI: 21-27%) at the time of the 6 month follow-up. At 14-months the sero-prevalence had dropped to 20% (p = 0.053, χ2-test, n = 998, 95% CI: 18-23%). Overall, this was a reduction in sero-prevalence compared with a study conducted in 2007 in the same area, where 31% (186/600) of pigs were found positive.
  
  
  CONCLUSIONS
  Confined pigs did not have a lower sero-prevalence compared to free roaming pigs in any of the three surveys. Several factors may have contributed to the observed fluctuations such as African swine fever or seasonal variation in local crop production practices. Also, as the Ag-ELISA assay used is not species specific, variation in transmission of Taenia hydatigena could potentially influence the results. The observed fluctuations contradict a theoretical model which predicts a stable equilibrium, which only considers a two-compartment (pig and human) model excluding the effect of the environment. Whether the disease has an endemic equilibrium, or undergoes fluctuations dependent on extrinsic and/or socio-economic factors remains to be elucidated.
authors.affiliation: Section for Parasitology and Aquatic Diseases, Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-1870, Frederiksberg, Denmark. braae@sund.ku.dk.
authors.forename: Uffe Christian
authors.initials: UC
authors.lastname: Braae
authors.affiliation: Section for Parasitology and Aquatic Diseases, Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-1870, Frederiksberg, Denmark. pma@sund.ku.dk.|Institute for International Health, Immunology and Microbiology, Centre for Medical Parasitology, University of Copenhagen, DK-1353, Copenhagen, Denmark. pma@sund.ku.dk.
authors.forename: Pascal
authors.initials: P
authors.lastname: Magnussen
authors.affiliation: Faculty of Agriculture, Sokoine University of Agriculture, Morogoro, Tanzania. lekulefp@yahoo.com.
authors.forename: Faustin
authors.initials: F
authors.lastname: Lekule
authors.affiliation: Faculty of Medicine, School of Public Health, Imperial College London, London, UK. w.harrison@imperial.ac.uk.
authors.forename: Wendy
authors.initials: W
authors.lastname: Harrison
authors.affiliation: Section for Parasitology and Aquatic Diseases, Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-1870, Frederiksberg, Denmark. mvj@sund.ku.dk.
authors.forename: Maria Vang
authors.initials: MV
authors.lastname: Johansen
mesh_terms: D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood; D003430:Cross-Sectional Studies; D003551:Cysticercosis / Q000097:blood / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D008137:Longitudinal Studies; D008297:Male; D015995:Prevalence; D016036:Seroepidemiologic Studies; D013552:Swine; D013553:Swine Diseases / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology / Q000469:parasitology; D041201:Taenia solium / Q000276:immunology / Q000302:isolation & purification* / Q000502:physiology; D013636:Tanzania / Q000453:epidemiology
chemical_list: D000909:Antibodies, Helminth