Article Type : Research Article
Authors : Yosef G, Kinfe H and Zewdu A
Keywords : Amhara region; Anthrax; Ethiopia; Human; Surveillance
Anthrax is an
infectious, bacterial zoonotic disease of warm-blooded animals including human
beings. This disease is caused by a spore-forming, aerobic, gram-positive, rod
shaped and non-motile bacterium (bacillus anthracis) [1]. When a spore enters a
mammal host, the internal environment of the host-rich in water, sugars and
amino acids-induces that spore to germinate into a vegetative cell that leads
to disease [2]. Infectious anthrax
spores are found naturally in soil and commonly affect domestic and wild
animals around the world [3]. An animal dying of anthrax produces enormous
quantities of the bacterium in its tissues. If the carcass is opened or when
exposed to open air of the hemorrhagic secretions or excretions, the vegetative
bacilli convert to resistant spores which contaminate the soil, grass, and
local water sources. Animals that graze in spore contaminated areas can become
infected, resulting in a further cycle of infection, death, and release of
spores to a new location. Wild carnivores and scavenger birds also contribute
to the spread of spores by feasting on contaminated carcasses [4].
Human
cases usually develop acutely after exposure to infected animals and their
tissues. The human cases are significantly associated with the animal disease. In most countries, human anthrax occurs
infrequently and sporadically, mainly as an occupational hazard among
veterinarians, agricultural workers, and workers who process hides, hair, wool
and bone products. Humans may exhibit three types of anthrax: cutaneous,
gastrointestinal and inhalational. Cutaneous anthrax is acquired when a spore
enters the skin through a cut or an abrasion; thus, anthrax scars are generally
seen on exposed regions of the body, mostly on the face, neck, hands and wrists
[5,6]. Cutaneous anthrax accounts for more than 95% of natural infections, and
is rarely fatal if treated with antibiotics. The gastrointestinal form is less
common but more serious, and can occur in outbreaks associated with eating
contaminated food, primarily meat from an animal that died of the disease.
Pulmonary (inhalational) anthrax, which is the most serious form and has a very
high case fatality rate even when treated, occurs from breathing in airborne
anthrax spores. Natural cases of inhalational anthrax are rare. The incubation
period in humans is usually 1 to 7 days, but varies with the form of the
disease [5].
Anthrax is distributed
worldwide. Although in developing countries the disease is endemic, most common
and human case rates for anthrax are highest; countries that do not have
veterinary public health programs that routinely vaccinate animals against
anthrax, in agricultural regions of several sub-Saharan African countries,
Central and South America, Middle East, central and southwestern Asia, southern
and Eastern Europe, and the Caribbean. Where the disease uncommon in animals,
but extremely rare in humans [7]. In Ethiopia, animal anthrax is an endemic
disease that occurs in May and June every year (‘anthrax season’) in several
farming localities of the country, causing disease both in humans and
livestock. Although suspected cases of anthrax are reported from several
districts, few of these are officially confirmed [8]. Previous
studies indicate that the disease is well recognized by rural communities but
little is known about its prevalence, epidemiology and public health
significance [9]. According to Federal Democratic Republic of Ethiopia
Ministry of Health surveillance data, in the Ethiopian fiscal year 2005
(Gregorian year 2012/2013), there were a total of 1,233 suspected human anthrax
cases and 15 deaths with a Case Fatality Rate (CFR) of 1.2% recorded in the
country. Cases were reported from four regions (Amhara, Tigray, SNNPR and
Oromiya). The most cases and deaths were reported from Amhara region [929 (75%)
cases and 8 (53%) deaths] [10]. Anthrax is a serious zoonotic disease that can
affect most mammals and several species of birds, as well as humans [11].
Anthrax is one of the twenty priority diseases under the Ethiopian Public
Health Emergency Management system that should be reported immediately when
encountered. Ongoing analysis of surveillance data is important for detecting
outbreaks and unexpected increases or decreases in disease occurrence,
monitoring disease trends, and evaluating the effectiveness of disease control
programs and policies. This information is also needed to determine the most
appropriate and efficient allocation of public health resources and personnel
[12].
Continuous surveillance and data analysis are
also important to evaluate the trends of anthrax related to intervention
measures in controlling and preventing of the disease. In Amhara region anthrax
is endemic, so it is an important public health issue and there is an apparent
need for accurate information through a strong surveillance system to warrant
evidence-based action. Therefore, analysing anthrax data can be used to assess
the trend of anthrax in the region and determine the distribution of cases.
This helps to identify areas to which anthrax is hyper endemic, and figure out
the completeness of the reporting system to engage in corrective actions.
Previous published information was not obtained which shows the status of human
anthrax in Amhara region. So, it was decisive to see the recent status of the
disease in the region; the main propose of this analysis was to assess the five
years (2013-2017) anthrax trend in the region in order to get valuable inputs
and recommend evidence-based interventions for the future. The objective of
this data analysis was to analyse and describe magnitude, trend, timeliness
rate, completeness rate, and limitations of anthrax surveillance data in Amhara
region from 2013-2017.
Study
area, population and period
The analysis was
conducted in Amhara region, which is one of the nine regional states of
Ethiopia, located in North Western part of the country. Bahir Dar is capital
city of the region. The region has an estimated land area of about 154,708.96
square kilometres. Amhara region is bordered by the state of Sudan to the West
and Northwest, and in other directions by other regions of Ethiopia: Tigray to
the North, Afar to the East, Benishangul-Gumuz to the West and Southwest, and
Oromia to the South. The region is administratively divided into 12 zones, and
140 Woredas. The recent population size predicted to be 21,134,988 of which
male 10,585,995 and female 10,548,993 in 2017. Five-year (2013-2017) anthrax
data were analysed from Jun - August 2018.
Source
of data
Amhara region five
years (2013-2017) human anthrax surveillance secondary data was obtained from
the data base of public health emergency management department of Ethiopian
Public Health Institute (PHEM/EPHI); from which we used to review human
anthrax. Human population was obtained from Ethiopian Central Statistics
Agency, 2007 census projection.
Study
design and data analysis
We conducted a
descriptive evaluation of Amhara region anthrax surveillance data during
2013-2017. The trend and distributions of anthrax cases during the time period
were calculated. The data was analysed using Microsoft office Excel 2007, and
the finding was presented by using tables and graphs.
Case
definitions
According to Ethiopian
Public Health Emergency Management Guideline, a suspected case of anthrax was
any person with acute onset of disease characterized by several clinical forms
which include [13]:
Suspected: Any person with acute onset characterized by several
clinical forms which are: -
Localized
form
Cutaneous: Skin lesion evolving over 1 to 6 days from a popular
through a vesicular stage, to a depressed black Escher invariably accompanied
by edema that may be mild to extensive.
Systemic
forms
Gastro-intestinal: Abdominal distress characterized by nausea,
vomiting, anorexia and followed by fever.
Pulmonary (inhalation): Brief prodrome resembling acute viral respiratory
illness, followed by rapid onset of hypoxia, dyspnoea and high temperature,
with x-ray evidence of mediastinal widening.
Meningeal: Acute onset of high fever possibly with convulsions,
loss of consciousness, Meningeal signs and symptoms; commonly noted in all
systemic infections and has an epidemiological link to confirmed or suspected
animal cases or contaminated animal products.
Ethical
consideration
First permission
approval was obtained from public health emergency management / EPHI then after
five years regional Anthrax data accessed to carry out this analysis.
Data
dissemination
Findings of the data were reported to St. Paul Hospital Millennium Medical College School of Public Health EFELTP, shared to EFELTP Resident advisor and coordinator of St. Paul Hospital Millennium Medical College and EPHI.
Magnitude
of anthrax in the region
During the last five
years (2013-2017), a total of 2,595 human anthrax cases and 24 deaths were
documented in Amhara region.
The
trend of human Anthrax cases by time
Cases by year: Of the total cases reported, most of cases 787(30.4%) and deaths 9(37.5%) occurred in 2013. The fewest cases371 (14.3%) occurred in 2017 and the fewest deaths 1(4.2%) occurred in 2015. Regionally, there was a continuous substantial decrease in the number of human anthrax cases, but there was fluctuation up on the number of deaths over the time period 2013–2017 (Figure 1).
Figure 1: Human anthrax cases
and deaths distribution by years (2013-2017), Amhara region, Ethiopia, 2018.
Cases by month: As we seen cases by month below in Figure 1, the
highest numbers of human anthrax cases were reported in the months of February
(285) and May (278), sum of the two months result account for 21.7% of the
total regional cases. A total of
1,067(41.1%) cases were reported in the first quarter (from January-April),
894(34.5%) in the second quarter (from May-August) and 634(24.4%) in the third
quarter (from September-December). The case report did not have regular trend
but from February to May it showed highest cases 1,106(42.6%) as shown in the
graph below Figure 2. The number of anthrax cases reported ranged from 138-285
cases for different months in the last five years. In particular, the monthly
trend showed an increase number of anthrax cases in month February-May of the
fiscal year reaching the high in February, whereas the anthrax cases decreased
from month May-December reaching the lowest in December [14].
Figure 2: Human anthrax cases by
month from 2013-2017, Amhara region, Ethiopia 2018.
Figure 3: Regional Anthrax Trend by WHO Epidemiological week, 2013-2017.
Cases by WHO epidemiological week: As shown in figure 2 below the largest
number of cases72, 52 and 42 were reported in week 7 0f 2014, week 10 of 2016 and
week 21 of 2013 respectively. Relatively the trend is showing highest number of
cases until week 23 of 2013. The trend of anthrax based on WHO Epidemiological
weeks was continues and no interruption was seen in the region from 2013 up to
2017; it indicates that anthrax was one of the burdens of the region for the
last five years (Figure 2).
The trend of human Anthrax cases by place: The number of human anthrax cases in
different zones and special woredas, range from 0 to 1,520. Zero (no) cases
were reported from Argoba Special Woreda and Bahir Dar Special Town. Nearly all
2,389(92.1%) cases were reported from Wag Himra, North Gondar, South Gonder,
and South Wollo zones. Of which Wag Himra reported 1,520(58.6%), north Gondar
524(20.2%), South Gonder 186(7.2%) and South Wollo 159(6.1%) cases, while the
least number of cases were reported from Dese Town 2(0.1%) followed by Awi
4(0.2%). During 2013-2017, human anthrax the highest case fatality rate (CFR %)
was seen in Oromia (28.6%) followed by South Wollo (5.0%) (Table 1).
In 2013 Wag-himra zone had highest number of cases, which were 458(17.6%) followed by North Gonder zone 153(5.9 %). In all years, Wag-himra zone had greater number of cases than other Zones/special woredas and also followed by North Gonder zone. Out of the total zones and special woredas of the region only 7 of them were reported the anthrax cases continuously without zero (no) report the whole of five years (Table 2).
Table 1: Anthrax Cases, deaths and CFR by Zones and special woredas of Amhara region, 2013-2017.
Zones/special woredas |
Cases (%) |
Deaths (%) |
CFR (%) |
Argoba Special Woreda |
0(0.0%) |
0(0.0%) |
0.00% |
Bahir Dar Liyu Town |
0(0.0%) |
0(0.0%) |
0.00% |
Dese Town |
2(0.1%) |
0(0.0%) |
0.00% |
Awi |
4(0.2%) |
0(0.0%) |
0.00% |
Oromiya |
7(0.3%) |
2(0.3%) |
28.60% |
West Gojjam |
17(0.7%) |
0(0.7%) |
0.00% |
North Wollo |
27(1.0%) |
0(1.0%) |
0.00% |
Gonder Town |
37(1.4%) |
0(1.4%) |
0.00% |
North Shewa |
47(1.8%) |
0(1.8%) |
0.00% |
East Gojjam |
65(2.5%) |
2(2.5%) |
3.10% |
South Wollo |
159(6.1%) |
8(6.1%) |
5.00% |
South Gonder |
186(7.2%) |
0(7.2%) |
0.00% |
North Gondar |
524(20.2%) |
6(20.2%) |
1.20% |
Wag Himra |
1,520(58.6%) |
6(58.6%) |
0.40% |
Grand Total |
2,595(100.0%) |
24(100.0%) |
1.60% |
Table 2: All human anthrax cases by year and Zones/special woredas of Amhara region, 2013-2017.
Zones/special woredas |
Years |
Grand Total | ||||
2013 |
2014 |
2015 |
2016 |
2017 | ||
Argoba Special Woreda |
0 |
0 |
0 |
0 |
0 |
0 |
Awi |
0 |
2 |
0 |
2 |
0 |
4 |
Bahir Dar special Town |
0 |
0 |
0 |
0 |
0 |
0 |
Desse Town |
0 |
1 |
0 |
0 |
1 |
2 |
East Gojjam |
29 |
14 |
4 |
3 |
15 |
65 |
Gonder Town |
17 |
6 |
3 |
5 |
6 |
37 |
North Gondar |
153 |
102 |
81 |
132 |
56 |
524 |
North Shewa |
34 |
2 |
1 |
4 |
6 |
47 |
North Wollo |
0 |
9 |
6 |
11 |
1 |
27 |
Oromiya |
1 |
6 |
0 |
0 |
0 |
7 |
South Gonder |
53 |
57 |
29 |
34 |
13 |
186 |
South Wollo |
42 |
92 |
6 |
8 |
11 |
159 |
Wag-Himra |
458 |
316 |
297 |
187 |
262 |
1520 |
West Gojjam |
0 |
2 |
1 |
14 |
0 |
17 |
Grand Total |
787 |
609 |
428 |
400 |
371 |
2595 |
The aim of this data analysis was to give a
description of human anthrax trend in Amhara regional state. This analysis
shows during the last five years (2013-2017) a total of 2,595 human anthrax
cases and 24 deaths were documented in region, which shows that the number of
human anthrax cases and deaths reported were increased by 23.2% and 60%
respectively than the previous national study [15]. The fatality of the case
between 2013 and 2017 in the region was higher (Case fatality rate 1.6%)
compared to previous national study (Case fatality rate 0.7%), this might be
due to the improvement of surveillance and reporting system of the region. The
highest number of cases 787(30.4%) and the lowest number of cases 371(14.3%)
were reported in 2013 and 2017 respectively. Results of retrospective data
analysis have indicated that there was an annual decreasing record of anthrax
cases in the region during the last five years (2013-2017). This might be due
to increased awareness of the community about the transmission of the disease,
improved health education in rural areas and increased vaccination coverage of
animals against anthrax. The highest numbers of human anthrax cases were
reported in the month of February (285) and May (278) cases, both of which
account 21.7% of the total cases. A total of 1,106(42.6%) cases were reported
from February to May. This is dry season, during this time the grass is short
and animals are, forced to graze very close to the ground. This increases
chances of animals picking up anthrax spores in areas whose soils and pastures
are contaminated with the spores [16]. Therefore, case of anthrax in animals is
very common during this time and as a result increasing risk of human anthrax
exposure. According to surveillance data analysis result the majority
2,389(92.1%) of the human anthrax cases were reported from four zones, of which
Wag-Himra reported highest number 1,520(58.6%) followed by North Gondar
524(20.2%). This might be due to culture, environmental factors and people’s
ways of life styles. Although B. anthraciscan be found worldwide, anthrax cases
usually occur only in limited geographic regions. Outbreaks are most common in
areas characterized by alkaline, calcareous soil (soil containing calcium
carbonate), a warm environment, and periodic episodes of flooding. Lifestyles
have very important effects on the disease patterns and health status of the
different places in the countries [17].
Our report had a few
limitations. First, the given data omitted the first 16 weeks of data from
Argoba special woreda during 2013. In addition, the weekly summary reporting
format for anthrax has no age, sex, or urban and rural distribution, which
prevents us from characterizing the pattern of disease reports by person.
Moreover, reported anthrax cases are not classified as suspected, probable, and
confirmed as per the WHO recommended case definition. Beyond this, the clinical
categories of the cases (cutaneous, inhalational, gastrointestinal, or
meningeal) were not reported. As a result, there were clear constraints in the
data collection and data quality to reach to strong conclusions and
recommendations.
Although there has been
an annual decline in numbers of cases and fatalities, during 2013-2017, anthrax
remains a major public health problem in Ethiopia, especially in Amhara region.
Human anthrax cases were more commonly recorded in the dry seasons (February-May)
than in other seasons. Among zones of the region increased numbers of cases
were reported especially from Wag-Himra, North Gondar, South Gonder, and South
Wollo zones. The regional health bureau should do sentinel surveillance in
Wag-Himra and North Gonder zone, from February-May. Control of anthrax depends
on the integration of animal and human health surveillance and control program.
So that targeted annual vaccination of livestock should be introduce based on
the level of disease endemicity before the onset of a known period of an
outbreak.
The authors would like
to acknowledge EFELTP, SPHMMC, EFMoH and EPHI department of PHEM. Our heartfelt gratitude also goes to those
individuals who are directly or indirectly contributed for the realization of
this analysis.