Challenges in assessing diagnostic test performance in a low-income country.

Kelly, R. (Speaker)

Activity: Academic talk or presentation typesOral presentation

Description

Development of a Fasciola gigantica modified serum antibody ELISA to estimate seroprevalence in Cameroonian cattle.

Cattle rearing is vital both economically and culturally to rural pastoral communities in many low-income countries, however parasitic diseases are often reported to detrimentally impact on cattle productivity. For example cattle infected with Fasciola species have reduced production, through development of subclinical or clinical fasciolosis. In tropical sub-Saharan Africa fasciolosis is thought to be attributed mainly to F. gigantica, although this is rarely confirmed. Cameroon has a large cattle population but few studies have been conducted to confirm which Fasciola species are present or to understand its local epidemiology. Serological assays are useful for quantifying exposure and identifying risk factors in natural infections, yet few are developed specifically for F. gigantica. As F. gigantica infections occur in cattle commonly in low-income countries, it is can be difficult to validate the performance of new assays in resource-limited settings. Such as where confirmatory diagnosis is infrequent or sample collection is logistically difficult. The aims of this project were to determine the Fasciola species infecting cattle in the main cattle rearing regions of Cameroon and develop a species specific serum ELISA. To demonstrate it is possible to validate the ELISA using naturally infected populations and then to use the ELISA to assess the seroprevalence of F. gigantica exposure in Cameroonian cattle.

A random sample of Fasciola parasites were collected from four Regional abattoirs in Cameroon and species determined using RAPD PCR analysis. Sixty whole parasites were identified as F. gigantica (100%, CI: 94.0-100 %). A F. gigantica serological ELISA was developed by collecting excretory/ secretory (E/S) antigen live adult parasites cultured for 24hours. Using a sample of known F. gigantica positive (n=20) and negative (n=72) cattle serum samples from Cameroonian and UK cattle populations the ELISA was deemed to be (85.0%) sensitive and (90.3%) specific. The assay’s performance was also assessed using Bayesian Non-Gold Standard methods using data collected during a study sampling 2064 cattle from two abattoirs in the North West Region (NWR) and Vina Division (VD) of Cameroon. Using data collected from animals exposed to in the field, the estimates for the assay’s sensitivity (67%) and specificity (67%) were refined to determine a positive cut off value that could be used in Cameroonian cattle.

Bovine seroprevalence of F. gigantica was assessed by conducting a stratified cross-sectional study was conducted in two cattle rearing areas of Cameroon, the NWR and VD, sampling cattle from 100 pastoral herds (n=1481 cattle). The seroprevalence of F. gigantica was higher in pastoral cattle in the VD (40.6%) than the NWR (6.47%).

Although there challenges of assessing the performance of livestock diagnostic tests in resource-limited settings, it can be possible using observational data from naturally infected populations. This project highlights that F. gigantica infection is endemic within Cameroonian cattle populations. Developing this assay could aid diagnosis and help design potential control strategies in infected herds.
Period29 Aug 2018
Event titleOne Health, Many Perspectives: Emerging Research from LMICs Symposium: Post Graduate & Early Career Researcher Symposium (ZELS)
Event typeConference
LocationLiverpool, United Kingdom
Degree of RecognitionInternational

Keywords

  • livestock
  • diagnostic test
  • parasitology
  • cattle
  • Fasciola
  • Cameroon
  • Africa
  • Pastoralist
  • infectious disease