TREND AND DISEASE BURDEN OF DYSENTERY IN ZAMBIA 2016-2018

BM Katemba, N Kayeyi, P Sakubita, A Ngomah Moraes, B Gianetti
Zambia National Public Health Institute ZNPHI

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Dysentery is bloody diarrhoea, i.e. any diarrhoeal episode in which the loose or watery stools contain visible red blood. Dysentery is most often caused by Shigella species (bacillary dysentery) or Entamoeba histolytica (amoebic dysentery) [1]. Over the past years, Dysentery has not stimulated public fear in the same way that Cholera has. Nonetheless, the disease can be extremely dangerous as it has the potential to affect a number of people in a short period of time. Just like Cholera, the disease is transmitted through ingestion of food or water that has been contaminated by the feces of a human carrier of the infective organism and can spread at a very fast rate. If not properly managed, Dysentery caused by Shigella dysenteriae type 1 (Sd1) can have a case fatality of up to 10% or more [2].

The disease has been recurrent in some parts of the world and is highly associated with high mortality in children [3]. Children below the age of 5 years and malnourished people [4] are mostly affected and are at a high risk of dying due to dysentery [5]. In 2015, Diarrhea diseases accounted for over 1.3 million deaths globally [6]. Dysentery caused by Shigella species (S. flexneri, S. sonnei, S. boydii, and S. dysenteriae) remains a major source of diarrhea in most developing countries.

In Africa, one of the earliest documented Dysentery cases caused by Sd1 was recorded in Burundi in 1943 [7]. Since then, Dysentery has remained a major public health problem in Sub-Saharan countries. In the 1980s, Rwanda and the Democratic Republic of Congo (DRC) recorded devastating dysentery cases that saw the community incidence of 5 % to 6.4%.

Since 1991, dysentery epidemics have occurred in eight countries in southern Africa (Angola, Burundi, Malawi, Mozambique, Rwanda, Tanzania, Zaire, and Zambia) [8]. In 1992, Zimbabwe was hit by dysentery outbreaks which affected almost all the provinces. However, 149 dysentery patients died (CFR 3%) out of 4 915 patients that presented themselves to two municipal hospitals [9].

A number of factors such as overcrowding and poor water and hygiene infrastructure [10], limited access to improved water supplies and sanitation facilities [11] are some of the prominent factors that contribute to dysentery outbreaks. Globally, contaminated water causes millions and millions of cases of dysentery every year [12].

In Zambia, there is little documentation and studies that have been done on dysentery. However, a few papers that have been done show that inter house sharing of latrines [13] and contact with a person who has dysentery are some of the risk factors to the spread of the disease. This paper presents dysentery trend analysis results analyzed from the Integrated Disease Surveillance and Response (IDSR) database.

Methodology

Reported dysentery suspected cases, confirmed and deaths were obtained from the IDSR weekly reports. Zambia is divided into 10 provinces; Lusaka, Western, Southern, Eastern, Copperbelt, Muchinga, Luapula, Northern, North-Western and Central province with a projected population of 16.8 million people [14].

In Zambia, Dysentery has been classified as a notifiable disease. All clinics and hospitals are required to report cases to the district surveillance officer. Data was entered and cleaned in Microsoft excel. Data on both clinical and laboratory confirmed cases were collected and analyzed in Microsoft excel. Additionally, this paper also retrospectively presents all dysentery related deaths as reported and confirmed in the IDSR reports. A spatial distribution of the three years in perspective was conducted using Tableau 2019.2. According to the IDSR, a suspected case is a person with diarrhea with visible blood in the stool while a confirmed case is a suspected case with stool culture positive for Shigella dysenteria type 1.

Results

In absolute terms, the highest number of cases have always been recorded in the fourth quarter of each year with 2016 recording 13450 suspected cases, 2017 (18866) and 2018 (15347). It’s generally observed that more confirmed cases (of the samples sent to the laboratory) are observed in Quarter 1 of each year; 2016 (88.2%), 2017 (72.6%) and 2018 (29.8%). According to the data collected, there was only one [1] dysentery related death for the period of three years (table 1)

Table 1 Descriptive Statistics of Reported Cases of Dysentery between 2016 and 2018 by quarter (Epi – 52 Weeks)

Note: Quarter 1 (Jan-Mar) | Quarter 2 (Apr-Jun) | Quarter 3 (Jul-Sep) | Quarter 4 (Oct-Dec) Figure 1 Trend of dysentery suspected cases by epidemiological week (2016-2018) In Zambia, the majority of dysentery suspected cases occurred during the summer (between 2016 and 208) which is mostly the rainy season corresponding to November to April (Fig 2). Suspected cases peak during epidemiological week 33 to week 44. A steady reduction of the suspected cases is noticed between week 45 and week 52. Generally, suspected cases tend to reduce between epidemiological week 8 through to week 32 with cases below 850 (2016-2018).
Figure 1 Trend of dysentery suspected cases by epidemiological week (2016-2018)
In absolute terms, three provinces (Central, Eastern and Southern) recorded above 20, 000 suspected dysentery cases between
2016 and 2018. Central province had the highest number of (28, 746) followed by Easter (25, 718) and Southern (22, 494) respectively.
Muchinga province recorded the lowest (4, 962) (Figure 2). From the samples sent for laboratory confirmation, Southern
province (381) recorded the highest number of positive cases while Central and Western province both had the lowest with 8 cases
(figure 2).

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In absolute terms, three provinces (Central, Eastern and Southern) recorded above 20, 000 suspected dysentery cases between
2016 and 2018. Central province had the highest number of (28, 746) followed by Easter (25, 718) and Southern (22, 494) respectively.
Muchinga province recorded the lowest (4, 962) (Figure 2). From the samples sent for laboratory confirmation, Southern
province (381) recorded the highest number of positive cases while Central and Western province both had the lowest with 8 cases
(figure 2).

Discussion
Incidence
The incidence rate of dysentery suspected
cases during 2016 to 2018 in Zambia
showed an overall increase. The lowest
rate (25.1 per 10,000 population) was
observed in 2016. This incidence is relatively
high compared to other countries
that have made tremendous efforts towards
improving the living conditions
(sanitation, water supply system etc). For
instance, in 2009, the incidence of dysentery
varied considerably from place to
place in China, with the highest incidence
of 14.2 per 10,000 in Beijing, and lowest
incidence being reported in Jiangsu and
Guangdong Provinces(15).

Suspected cases vs. confirmed
The Zambia National Public Health Institute
throw its surveillance cluster has
continuously been collecting data on cases
from well-trained surveillance officers
and clinicians. Additionally, laboratory
technicians across the country have been
adequately trained to identify Shigella
species. Therefore, it is expected that data
presented on the cases is a true representative
picture of what is prevailing at provincial
level.

In countries with scarce resources like
Zambia, the role of the laboratory is to use
those resources to provide the best information
for developing treatment policy,
rather than to focus on the diagnosis of individual
patients. However, there is still a
huge disparity in the suspected cases and
samples sent for laboratory confirmation
(16). Continued sensitization of healthcare
workers about dysenetry case definitions
and reporting procedures could also
help increase the proportion of suspected
dysentery cases for whom samples are
collected and sent for laboratory confirmation.
Different studies have acknowledged how
difficult it is to clinically distinguish between
non-bloody diarrheas caused by
Shigella dysenteriae from diarrhea caused
by other enteric pathogens. This could
possibly explain the huge discrepancy between
suspected cases and samples sent
for laboratory confirmation.

Seasonality
Between 2016 and 2018, the majority of
dysentery cases were recorded during
summer months. A retrospective study
done in China for the years between 1991

to 2000 established that the majority of
the dysentery cases were recorded during
the months of summer(Wang, 2006). In
Vietnam, incidences of dysentery are significantly
high during the wet season particulary
between May and October (17)
(18) (19) (20).
Different studies have shown that the hot
season provides a suitable environment
for the growth of bacteria (17) (15) (21).
This study shows that the peak period for
dysentery suspected cases is in October
which is generally the peak of the hot season
in Zambia.

Geographic location
Central province has the highest recorded
suspected cases in all the three
years (2016-2018). According to the
koppen-Geiger climate classification of
1980-2016, this area is characterized by
dry winter and hot summer with temperature
ranging from 21.4°C to 29.3°C
(22). A study done in Kon Tam Province in
Vietnam from 1999 to 2013 showed that
there was a correlation between weather
change and dysentery cases. Findings of
the study showed that a 1 °C increase in
temperature increased the incidence of
dysentery cases by 6% (17).

Conclusion
The incidence of dysentery suspected
cases remains high in Zambia. With increasing
antimicrobial-resistant on Shigella
bacteria, there is need to scale up
preventive interventions to Central province
in order to see the much needed reduction
of dysentery cases. Prevention of
Shigella infections through vaccination or
improvements in safe drinking water and
sanitation would be the long-term solution.
However, as a short term measure,
continued health education on dysentery
risk factors and provision of clean and
safe water should be prioritized in areas
with high cases.

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