Impact Of Flood On Waterborne Bacterial Pathogens. A Study In Anambra River: South East, Nigeria.

ABSTRACT

A cross sectional and retrospective study was carried out to assess the impact of flood on

waterborne bacterial pathogens in Anambra River. Under conditions of climate change, heavy

rain and flood would increase the risk of faecal contamination of surface and ground water. This

increases the risk of waterborne zoonoses. Waterborne infections result from drinking water

contaminated by pathogens such as E. coli and Salmonella discharged from human or animal

excreta. The objectives of this study were to quantify the bacterial load of water of Anambra

River affected by flood used for household purposes and washing of meat and of meat in the

slaughter slabs before and after washing with water from the River; isolate waterborne

Salmonellae and E.coli serotypes in the flood water and meat before and after washing, and

assess and compare the prevalence of human diarrheic infections before, during and after the

period of flood as recorded by the hospitals in the area. Flood water from where the residents

collect for household purpose; flood water used for washing of meat at slaughter slab; samples of

meat before and after washing with the flood water were collected for 18 weeks. Serial dilutions

of each sample were made. Total Viable Bacterial Counts and Coliform Counts were done, using

Pour Plate Method in Nutrient Agar and MacConkey Agar, respectively. Mean bacterial load of

the various samples were calculated for the periods of the flood. Isolation and identification of

E.coli and Salmonella from water and meat were performed following the standard

microbiological technique. Biodata on confirmed diarrheic and gastrointestinal patients were

abstracted from the comprehensive records of the Catholic Diocesan Hospital and General

Hospital, Umuleri from January 2011 to December 2013. Data generated were subjected to

statistical analysis (Chi square and paired t-test). Questionnaire survey of residents of Umuleri

Community regarding periods of flood of Anambra River in the last three years indicated as

follows; June/July rising of flood; Aug/Sept peak of flood; Oct/Nov receding of flood and

Dec/Jan normal water level. Generally the bacterial load of the flood water at point of collection

for household purpose, the bacterial load of water used for washing of meat, and the bacterial

load of meat before and after washing was high ranging from 2.7x108 to 2.8x1016cfu/ml. There is

significant difference (t=2.930; p=0.033) in the mean Total Viable Bacterial Counts between

peak of flood (Aug/Sept) and normal water level (Dec/Jan) at point of water collection for

household purposes. There is also significant difference (t=2.769; p=0.039) in the mean Total

Viable Bacterial Counts between the peak of flood (Aug/Sept) and normal water level period

(Dec/Jan) at point of water collection for washing of meat. The mean bacterial load of meat after

washing with the flood water (8.0x1012 ± 1.4 cfu/g) was significantly (p=0.020) higher than

before washing (7.95x1011 ± 12.25 cfu/g). There is also significant difference (t=3.005; p=0.030)

in the mean coliform count between peak of flood (Aug/Sept) and normal water level (Dec/Jan)

at point of water collection for household purposes. There is also significant difference (t=2.945;

p=0.032) in the mean coliform count between the peak of flood (Aug/Sept) and normal water

level period (Dec/Jan) at point of collection of water for washing of meat and slaughter facilities.

The mean coliform count (cfu/g) of meat after washing (5.67x1010 ± 82.57) was significantly

(p=0.013) higher than before washing (4.12x109± 4.96). Verotoxigenic E. coli and Salmonella

spp were isolated from the flood water and from meat samples before and after washing with the

flood water. Out of a total of 433 confirmed diarrheic cases registered in two hospitals, 228

(53%) were registered in 2012 when Nigeria experienced the worst flooding in recent years. In

conclusion flood resulting from climate change, increases the risk of waterborne infection from

flood water and meat at slaughter slab.