Clinical and Environmental Surveillance for Vibrio cholerae in Resource Constrained Areas: Application During a 1-Year Surveillance in the Far North Region of Cameroon

Abstract

Biological confirmation of the presence of Vibrio cholerae in clinical and environmental samples is often constrained due to resource- and labor-intensive gold standard methods. To develop low-cost, simple, and sustainable surveillance techniques, we modified previously published specimen sampling and culture techniques and applied the use of enriched dipstick testing in conjunction with the use of filter paper for DNA specimen preservation during clinical and environmental surveillance in the Far North of Cameroon from August 2013 to October 2014. The enriched dipstick methodology during routine use in a remote setting demonstrated a specificity of 99.8% compared with polymerase chain reaction (PCR). The novel application of filter paper as a preservation method for cholera DNA specimens reduced the need for cold chain storage and allowed for PCR characterization and confirmation of V. cholerae. The application of basic technologies such as the enriched dipstick, the use of simplified gauze filtration for environmental sample collection, and the use of filter paper for sample preservation enabled early case identification with reduced logistics and supply cost while reporting minimal false-positive results. Simplified laboratory and epidemiological methodologies can improve the feasibility of cholera surveillance in rural and resource-constrained areas, facilitating early case detection and rapid response implementation.

Cholera Rapid Test with Enrichment Step Has Diagnostic Performance Equivalent to Culture

“…This field evaluation of the enriched rapid test for diagnosis of cholera confirmed initial reports suggesting that the APW incubation step ensures high specificity, which improves confidence in the test results and could diminish the risk of false cholera outbreak alerts [13,14]. Incubation in APW for 4–6 hours is also the first step in laboratory methods used for the diagnosis of V .…”

“…However, in this study, the performance of the direct test was not consistent with previously published studies, with low sensitivity (65%) and high specificity (92%); the reasons for these discrepancies were not discussed, but could be due to the addition of a step of dilution of the stools in a sample preparation vial. Another study confirmed the high specificity of RDT after enrichment in APW but sensitivity could not be reliably estimated due to the low number of confirmed cholera cases [14]. …”

Rapid dipstick detection of Vibrio cholerae in household stored and municipal water in Dhaka, Bangladesh: CHoBI7 trial

“…Beyond the recent study in Bangladesh, there is only one other study to our knowledge that has used the Crystal VC ® dipstick test for the detection of V. cholerae in water. This study, conducted in Northern Cameroon, found a specificity of 100% in comparison with PCR, but had insufficient numbers of positive water samples to calculate sensitivity .…”

“…Culturing is considered to be the gold standard for detecting V. cholerae but requires skilled technicians and a laboratory facility, which is often not feasible in resource-limited settings [9][10][11][12]. Recently, a rapid dipstick test, for detection of V. cholerae (Crystal VC â kit, Span Diagnostics Ltd., Surat, India), was introduced and validated for detecting the pathogen from stool and environmental water samples [13][14][15][16][17][18][19][20]. However, to our knowledge, no study has been carried out to validate the use of this dipstick test for conducting household surveillance of V. cholerae in stored water samples.…”

Highlights of the 8th International Conference on Vaccines for Enteric Diseases: the Scottish Encounter To Defeat Diarrheal Diseases

“…The audience learned from Martin Mengel, from Agence Medicine Preventive, Paris, that further efforts to understand the distribution of cholera in Africa have been undertaken by AfriChol, the African Cholera Surveillance Network (19). To further understand disease transmission patterns, Amanda Debes from the JHU Bloomberg School of Public Health described a combined clinical and environmental surveillance of Vibrio cholerae for resourcelimited areas that involves testing of clinical specimens with a rapid dipstick assay (crystal V. cholerae; Span Diagnostics Ltd., India), after alkaline peptone water (APW) enrichment, and blotting onto filter paper for subsequent analysis using molecular methods (20,21). This method was successfully used in the far north region of Cameroon and enabled early detection of cases and rapid response (21).…”