ABSTRACT
Objectives: To determine some
epidemiological aspects of imported malaria cases among Jordanians and
non-Jordanians who returned to Jordan
from endemic areas and to highlight the importance of compliance with
prophylaxis against this disease and identify the type of plasmodium species causing
the disease.
Methods: This is a descriptive study
of the imported malaria cases registered at Malaria and Bilharzia Division, Ministry
of Health in Jordan.
The study included all people registered and tested for malaria at Malaria
Division between January 2000 and December 2005. All subjects gave a peripheral
blood sample to detect malaria parasite by thick smear method.
Results: From 2000 to 2005, out of 304,314 blood
smears, 808 had positive results (detection of malaria parasites) in their
blood sample. Out of the total number of 808 cases 606 (75%) were infected with
plasmodium vivax, 201 (24.9%) with plasmodium falciparum, one (0.1%) subject
had mixed infection. There were no positive cases of plasmodium malarie in our
study period. The geographic distributions of these imported cases were mainly
from East Africa (Sudan and Eritrea) and South East Asia (Timor).
Jordanian nationals constituted 589 (72.9%) cases and the majority of them were
military personnel who participated in Peace Keeping Forces all over the world.
Conclusion: The continued presence of imported malaria in Jordan calls for emphasis on effective prophylaxis
especially among Jordanian Peace Keeping Forces to prevent resurgence of this
disease and to keep Jordan
at a low incidence of malaria.
Key words: Epidemiology, Imported, Malaria
JRMS
December 2009; 16(3): 10-15
Introduction
Four species of the protozoan parasite
plasmodium infect humans. P. falciparum can cause a lethal infection, whereas
P. vivax, P. malariae, and P. ovale cause milder but nonetheless debilitating
acute disease. P. vivax and P. falciparum are the most abundant species; P. ovale
is the rarest.(1) Beside the clinical suspicion of malaria,
the diagnosis is made via microscopic examination of thick and thin blood
smears. The thick blood smear is more sensitive in detecting malaria parasites
because the blood is more concentrated allowing for a greater volume of blood
to be examined. However, thick smears are more difficult to read. Laboratories
that have limited experience may prefer to use thin smear, which can aid in
parasitic species identification.(2)
While primary malaria transmission was successfully
interrupted in many countries including Jordan, malaria (falciparum and
vivax) remains a constant health threat for travelers
to other malarious areas. These travelers may become symptomatic during their stay in these localities or after they return to their home country.(3) The risk of malaria infection to travelers is increasing; each year 25-30 million people from non-tropical countries visit areas in which malaria is endemic, of whom between 10,000 to 30,000 contact the disease.(4) As many Jordanians are visiting endemic malarious areas, it is certainly worthwhile to screen for this disease among them to avoid unnecessary complications caused by missing the correct diagnosis.
Table I. No. of positive samples, species of P. Malaria
(2000-2005)
|
Year
|
No. of
|
No. of Positive
|
Type of Plasmodium
|
|
Samples
|
Samples
|
P.Falciparum
|
P.Vivax
|
Mixed
|
|
2000
|
55279
|
148
|
42
|
105
|
1
|
|
2001
|
59235
|
131
|
50
|
81
|
0
|
|
2002
|
57700
|
143
|
31
|
112
|
0
|
|
2003
|
54658
|
144
|
26
|
118
|
0
|
|
2004
|
47363
|
160
|
41
|
119
|
0
|
|
2005
|
30079
|
82
|
11
|
71
|
0
|
|
Total
|
304314
|
808
|
201
|
606
|
1
|
|
Percentage
|
|
|
24.9
|
75.0
|
0.1
|
Table
II. Imported Malaria Cases by Age
Group (2000-2005)
|
Age Group/Years
|
Year
|
Total
|
|
2000
|
2001
|
2002
|
2003
|
2004
|
2005
|
Number
|
Percent
|
|
16 - 25
|
44
|
36
|
32
|
41
|
39
|
23
|
215
|
26.6
|
|
26 - 35
|
79
|
69
|
80
|
78
|
101
|
40
|
447
|
55.3
|
|
36 - 45
|
22
|
19
|
26
|
20
|
16
|
17
|
120
|
14.9
|
|
More than 45
|
3
|
7
|
5
|
5
|
4
|
2
|
26
|
3.2
|
|
Total
|
148
|
131
|
143
|
144
|
160
|
82
|
808
|
|
Methods
Malaria and Bilharzia Division is responsible
for planning and implementation of malaria control programme, strategies and
activities including control of the mosquito vector, detection and treatment of
imported malaria cases and all other cases (like introduce or injected). The Malaria and Bilharzia Division has maintained
continuous surveillance of Plasmodium infections among arrivals utilizing their
teams at border entry stations of the country. All entering subjects underwent
a thick blood smear test after verbal consent regarding previous malaria
infection, the endemic area they arrived from, and their residency address to follow
them up, for treating them if they were infected.
A retrospective review over a period of 6
years, from January 2000 to December 2005 was done, during which all imported
malaria cases were followed closely with early diagnosis, proper treatment and followed
up by monthly visits to the Malaria and Bilharzia Division for at least one
year duration.
Results
During the study period a total of 304,314
blood samples were taken from individuals arriving in Jordan from endemic areas. Eight
hundred and eight cases of imported malaria were identified. Out of this
number, a total of 201 (24.9%) cases were caused by P. falciparum, 606 (75%) by
P. vivax, one (0.1%) case by mixed malaria infection. There was no reported
case of P. malarie in our study period (see Table I).
There were 775 (95.9%) males and 33 (4.1%)
females with a mean age of 30.4 ± 8.1 (range, 16 – 58) years as shown in Tables
II.
Table III shows the geographic distribution of
imported cases, from a total number of 808 positive samples: 72 (8.9%)cases
were from West Africa , 340(42.1%)cases from East Africa, 84(10.4%) cases from Central Africa,
1(0.1%)cases from South Africa, 3 (0.4%) cases from North Africa, 67(8.3%)
cases from south Asia,153(18.9%) cases from South East Asia,47(5.8%) cases from
Middle East, 2 (0.2%) cases from the Caribbean and 39 (4.8%) cases had no
available data for their source. There were no documented cases from North
Asia, East Asia and Central\South
America.
As shown in Table IV, Jordanians constitute
72.9% (n=589) and 27.1% (n=219) were non-Jordanians. The majority
of Jordanians
were participants
in
Table
III. Imported Malaria Cases by Travel
Area#
|
Geographic area *
|
Year
|
Total
|
|
2000
|
2001
|
2002
|
2003
|
2004
|
2005
|
Number
|
Percent
|
|
West Africa
|
12
|
27
|
2
|
8
|
15
|
8
|
72
|
8.9
|
|
East Africa
|
…
|
11
|
73
|
94
|
104
|
58
|
340
|
42.1
|
|
Central Africa
|
22
|
16
|
18
|
6
|
17
|
5
|
84
|
10.4
|
|
South
Africa
|
…
|
1
|
…
|
…
|
…
|
…
|
1
|
0.1
|
|
North Africa
|
2
|
…
|
1
|
…
|
…
|
…
|
3
|
0.4
|
|
South Asia
|
14
|
13
|
8
|
12
|
15
|
5
|
67
|
8.3
|
|
South East Asia
|
77
|
43
|
25
|
8
|
…
|
…
|
153
|
18.9
|
|
Middle East
|
17
|
9
|
9
|
7
|
3
|
2
|
47
|
5.8
|
|
Caribbean
|
…
|
…
|
…
|
…
|
…
|
2
|
2
|
0.2
|
|
Not given
|
4
|
11
|
7
|
9
|
6
|
2
|
39
|
4.8
|
|
Total
|
148
|
131
|
143
|
144
|
160
|
82
|
808
|
100 **
|
#According
to Centers for Disease Control and Prevention, Department of Health and Human
Services division areas
*There are
no documented cases from North Asia and Central / South
America
**Totals do
not add to 100%
Table
IV. Imported Cases by Nationality
|
Year
|
Total cases
|
Jordanian
|
Non-Jordanian
|
|
Cases
|
Percent
|
Cases
|
Percent
|
|
2000
|
148
|
92
|
62.2
|
56
|
37.8
|
|
2001
|
131
|
95
|
72.5
|
36
|
27.5
|
|
2002
|
143
|
106
|
74.1
|
37
|
25.9
|
|
2003
|
144
|
107
|
74.3
|
37
|
25.7
|
|
2004
|
160
|
121
|
75.6
|
39
|
24.4
|
|
2005
|
82
|
68
|
82.9
|
14
|
17.1
|
|
Total
|
808
|
589
|
72.9
|
219
|
27.1 |
United Nations (UN) Peace Keeping Missions and the majority of the
non-Jordanians were from Sudan,
Yemen, Sri Lanka and Pakistan.
Out of the 75% of cases which were caused by P.
vivax, the majority originated from South Asia (India,
Pakistan, and Sri Lanka) and Central Africa (Sudan). Sudan
was a major source of malaria imported from Central Africa
in this study: 74 cases were imported from there, 62 patients were Sudanese and
12 patients were Jordanians. P.falciparum
constituted 24.9% of recorded cases; most of them were from East and West Africa.
Out of 808 cases, 500 (61.95%) cases were from
Africa, from which, there were 340 cases from East Africa with the vast
majority (n=336) from Eritrea,
all of them were Jordanians who participated in UN Peace Keeping missions.
The majority of cases reported from West Africa
were from Sierra Leone
with 34 cases out of 72 (47.2%), and also all of them were Jordanians who
participated in the UN Peace Keeping missions.
In our study, 0.1% (n=1) of cases was caused by
mixed malaria infection, this patient showed P. falciparum and P. vivax in his
blood smear. P. malariae was not diagnosed in our study period, but had been
identified in prior years 1997, 1998 and 1999 with number of 2, 1, 1 cases
respectively. P. ovale was not isolated at Ministry of Health over the study
period.
South East Asia contributed 18.9% (n=153) of
malaria cases, with around 95% (n=146) of cases were from Timor.
All patients from Timor were Jordanians who
participated in UN Peace Keeping missions.
Discussion
Despite 50 years of eradication efforts,
malaria remains a major scourge throughout the tropics. The disease is becoming
increasingly common, with 300 million to 500 million new infections and 1.5 to
2.7 million deaths, mainly children, occurring every year.(2,3)
The geographic distribution of malaria depends mainly on climatic factors such
as temperature, humidity, and rainfall. In warm regions close to the equator
transmission is more intense, occurs around the year and is predominantly with
P. falciparum, while in cooler regions, transmission is less intense and more
seasonal and P. vivax prevails because it is more tolerant of lower ambient
temperatures.(5) At
least 90 countries in Africa, Asia, the Caribbean, Central and South America
are officially considered malarious.(6) Ninety
percent of malaria cases and deaths are believed to occur in sub-Saharan
Africa, and in many areas the disease is
spreading through the local population and also to travelers. In west Africa,
without prophylaxis, malaria is estimated to have an incidence of 1.4% per
person per month and travelers to west or east Africa have the chance to
contract the disease by 2-4% per month due to lack of partial immunity that is
achieved by previous attacks of malaria.(7,8) The risk that a
traveler will become infected depends on the overall rate of malaria
transmission in the area visited and the extent of the traveler's contact with
infected mosquitoes.
Transmission rates may vary greatly from region to region
even within the same country, thus, the route and mode of travel and
destination are important considerations. Furthermore, since the rate of
transmission of malaria may vary from season to season in the same region, the
timing of travel may also influence the risk. Finally, since female anopheline
mosquitoes feed from dusk to dawn, the risk is influenced by a traveler's
nighttime activities and the characteristics of his or her lodging.(1)
The spread of drug-resistant strains of P. falciparum
since the 1960s has reduced the efficacy of chloroquine, which for several
decades was a highly effective, convenient, and relatively safe prophylactic
and therapeutic drug. The combination of pyrimethamine and sulfadoxine and
amodiaquine were introduced as alternative chemoprophylactic agents, but both
proved to be too toxic to be widely recommended for this purpose. Subsequently,
mefloquine became available as an effective chemoprophylactic drug against
chloroquine-resistant P. falciparum. Doxycycline also proved useful for this
purpose.(1, 9-11)
No currently available regimen of
chemoprophylaxis against malaria is completely effective, and drug resistance
continues to evolve. The potential for serious toxicity with these
anti-malarial agents is perhaps the greatest concern and necessitates a careful
review of travel plans to assess risk versus benefit. Even minor side effects
adversely affect compliance, and many vulnerable travelers never complete their
recommended prophylactic regimen.(12) accordingly careful attentions
to avoid contact with mosquitoes are an additional and essential facet of
malaria prevention.
While malaria transmission was successfully
interrupted in the United States (US) during the late 1940s, malaria remains a
constant health threat for US travelers to malarious areas. In 2004, 1324 cases
of malaria were reported in the USA,
P. falciparum identified in 50% of them. Seven hundred and seventy five cases
out of 1324 occurred in civilians, all of which were imported, 65% of them did
not take any chemoprophylaxis and only 20% were compliant with the regimen
recommended by the Center for Disease Control and Prevention (CDC) for the area
in which they traveled. Eighty-eight percent of patients with imported malaria
reported symptom onset after arriving back in the USA and 73% of imported cases
occurred in persons who traveled to Africa.(2,13)
In a retrospective study done by Brustenga for
the years 2002 to 2004 in Spain showed that P. falciparum is the most diagnosed
species and Africa is the continent from which most cases are imported.(14)
In another retrospective study, done by Ong and Smyth for imported malaria
cases in Northern Ireland between the years 1998 and 2003 showed that P. falciparum
was the most common infection (60%). This was particularly associated with
travel to West Africa. Most cases were
associated with short visits to malarious areas. Thirty-three percent of cases
did not take prophylaxis and of those that did, approximately half were taking
a prophylactic regimen appropriate to the region visited.(15)
Sudan is one of the unusual regions in Africa
where all four plasmodium species are found, with the frequency of the species
varying according to different studies and to epidemiological zones of the
country,(16) malaria
is considered a leading cause of
morbidity and mortality in Sudan, and the entire population is at risk of
malaria, although to different degrees. In northern, eastern and western states
of the Sudan
malaria is mainly low to moderate with predominantly seasonal transmission and
epidemic outbreaks. In southern Sudan,
malaria is moderate to high or highly intense, generally with perennial
transmission.(17) In a retrospective study done by Alkhalife
of imported malaria infection diagnosed at the Malaria Referral Laboratory in Riyadh, Saudi Arabia,
showed that although P. falciparum counted for about 90% of cases coming from
Sudan, there was a high proportion of infection caused by P. vivax.(18)
Two studies conducted in Sierra Leone in 1992
and 1994 showed that cases caused by P. falciparum constituted 61% and 90.4%
respectively.(19) In two retrospective studies done in Sierra
Leone, of Jordanian medical teams participating in UN missions in the years
2000 and 2002 showed that despite emphasized compliance with mefloquine
prophylaxis among the members of the missions, 5% (38 malaria cases among 760
participants) and 15.1% (18 malaria cases
among 119 participants ) of malaria were reported respectively. This failure
rate of chemoprophylaxis may be explained either as patient's non-compliance or
the presence of a Mefloquine-resistant strains.(7,20)
In Eritrea, malaria is spread over 75% of the
surface of the country,(21) and according to Masale et al.
malaria affects two thirds of the population with P. falciparum predominating
at 90% and P. vivax at 10%.(22)
The vast majority of cases in our study from South
East Asia were from Timor, which has a very high risk for malaria all over its
regions,(23) and the majority of patients from
South Asia were Pakistanis, Indians and Sri Lankans with a predominance of P. vivax
species which is expected because it is the predominant species of malaria in
their respective home countries.(24-26)
In the United Kingdom, there are 1500-2000
imported cases reported each year, and 10-20 deaths. Three-quarters of reported
malaria cases are caused by P. falciparum, others caused by P. vivax, a few
cases are caused by P. ovale and P. malariae, although mixed infections with
more than one species of parasite can occur.(27)
Conclusions
Malaria with its different species is being
imported to Jordan by
Jordanians participating in peace keeping missions in different parts of the
world, mainly Africa and Asia and by non Jordanians visiting Jordan for work or tourism. Caution
must be exerted to avoid the reintroduction of this deadly disease which was
eradicated in Jordan
many years ago.
The participants in peace keeping missions must
be properly educated about the seriousness of the issue of taking prophylactic
medications. It is also important to remember
the role of antimosquito measures
in preventing the disease. The possibility of importation of malarious
mosquitoes on aircraft coming from endemic areas should also be remembered.
Acknowledgement
Special thanks to the continuous efforts exerted by the Ministry of
Health, the Department of Malaria and Bilharzia, to keep Jordan a malaria-free country,
despite some few imported cases that are discovered and treated promptly.
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