Incidence of Human Malaria Infection in Northern Hilly Region of Balochistan, Adjoining with NWFP, Pakistan: District Zhob

Malaria is one of the most devastating diseases in the World. Over 3 billion people live under the threat of malaria in 24 endemic countries (WHO/UNICEF, World Malaria Report, 2005) and it kills over a million each year- mostly children (Korenromp, 2004).

Falciparum and vivax malaria are major health problems in Pakistan. In the last decade there has been a six fold increase in falciparum malaria, which now comprises 42% of all malaria cases recorded by National Malaria Control Program (MCP) (Shah et al.,1997). Factors associated with the upsurge include of chloroquine resistance across the country (Shah et al., 1997), warmer autumns favoring prolonged transmission (Bouma et al., 1996) and a chronic decline in vector control activities. Anopheles culicifacies, the purported primary vector in the Punjab Province (Reisen and Borham, 1982) was found more or less disappeared by September whereas A. stephensi was found more abundant and more common in North-West Frontier Province than A. culicifacies. In Pakistan, the primary vector species are A. culicifacies and A. stephensi and in Quetta Balochistan also (Malaria Control Program, 1999, 2000; Yasinzai and Kakarsulemankhel, 2003).

In Pakistan, Hozhabri et al. (2002) studied prevalence of plasmodium slide positivity among the children treated for malaria at Rural Health Center (RHC) Jhangara, Sindh and observed slide positivity rate 5.9% (26/438). Bhalli and Samiullah (2001) investigated a review of 120 cases of falciparum malaria at CMH, Multan to evaluate seasonal variation and modes of presentation. They observed high incidence of falciparum malaria among troops in the moths of August to November. Akbar (2002) reported malaria at a children hospital Baqai Medical University and observed high incidence of Falciparum as compared to vivax (65 vs 35%). Mohammad and Hussain (2003) studied prevalence of malaria in general population of district Buner and highest rate of infection (11.6%) was recorded in August while the lowest rate of infection (3.9%) was noted in March. Malaria in pediatric age group of 200 cases was investigated by Jamal et al. (2005) and found high rate of P. vivax (62.5%) than P. falciparum. (36%). Nizamani et al. (2006) found that P. falciparum ratio was noted to be increasing in many districts of Sindh. Malaria in North West Frontier Province (NWFP) was studied by Saleem et al. (2006) and observed cerebral malaria more common in males and most vulnerable group was pregnant ladies. Jalaluddin et al. (2006) investigated malaria in children in Mansehra and observed 142 cases suffering from vivax and 12 from falciparum out of 160 cases. Idris et al. (2007) while studying pattern of malarial infection at Ayub Teaching Hospital Abbottabad found that out of 1994 patients screened, 145 (7.2%) were found infected. P. vivax was seen in the majority (72.4%) than P. falciparum (24.1%).

In Balochistan too, cerebral malaria is a major community problem. Nawaz and Yasmin (1987) studied the prevalence of malaria in Afghan refugees settled in urban areas of district Quetta. Durrani et al. (1997) studied epidemiology of cerebral malaria and its mortality in patients of Quetta city. Malaria at Zhob Garrison was studied by Khadim (2002) during the years 2000 and 2001 and found 665 patients positive for malaria out of 5650 cases. Yasinzai and Kakarsulemankhel (2003, 2004) investigated the incidence of malaria infection in urban and rural areas of Quetta district. Malaria Control Program (MCP) Balochistan in its yearly reports showed positivity rate 10.1%, P. vivax 6.6%, P. falciparum 3.5, 11.2, 6.6, 4.6 and 12.7, 8.2, 4.4% in 2004, 2005 and 2006, respectively (Malaria Control Program, 2004, 2005, 2006). Sheikh et al. (2005) observed slide positivity 34.8% (91679/2, 63, 018) in Quetta during 1994-1998. While studying malaria in central areas of Balochistan (Mastung, Khuzdar districts), Yasinzai and Kakarsulemankhel (2007) observed 2092 (26.6%) confirmed cases of malaria out of 7852 in the year 2004-2006. In Zhob district where malaria cases are seen throughout the year according to Khadim (2002) who studied malaria cases of Zhob Garrison reported at Combined Military Hospital (CMH) Zhob which does not represent the situation of malaria in the whole district. Therefore, in the present study the incidence of malaria in the whole district comprising 37 localities along with seasonal variation of the disease has been investigated.

A survey was conducted during July, 2004 to June, 2006 in 37 localities of district of Zhob to record and screen species of malarial parasites from the blood of human patients suffering from malaria.

Location: District Zhob (Lat. 30°, Long. 68°, Height 1410 m) is situated at the north-eastern border of Balochistan province adjoining in the west with Afghanistan and in the east with Dera Ismail Khan area of the NWFP (Pakistan) where cases of human malaria are very frequent.

Malaria cases were detected by adapting two ways (Manson-Bahr and Bell, 1987). Passive Case Detection (PCD) technique where in blood films were taken from the patients presenting themselves to a health station with symptoms of shivering and fever or a history suggestive to malaria. The other technique is Active Case Detection (ACD) in which home visits were made to the persons with sign or symptoms of malaria and blood films of both thin and thick were prepared. Blood slides were taken back to the laboratory where they were stained in Giemsa`s stain following the techniques described by Manson-Bahr and Bell (1987). Identification of species of malarial parasites were made from the keys furnished by Service (1986) and Sood (1989). Statistical analysis of the data (Chi-square test) on the overall incidence of malaria infection was also applied.

A total of 7748 blood smears were prepared from the age groups ranging from 1 year to 21 years and above, residing in different localities of Zhob (Table 1-4). However, variations of infection with P. vivax

Table 1:	Area and over all incidence of malaria infection in Zhob district

Table 2:	Month wise and over all incidence of malaria infection in Zhob district

Table 3A:	Age-wise over all incidence of malaria infection in Zhob district

Table 3B:	Statistical analysis of Table 3A age-wise over all incidence of malaria infection in Zhob district
fo = 1st and 2nd column show the incidence rate of P. vivax and P. falciparum, respectively. fe = 1st and 2nd column show the % of infection of both the columns

Table 4:	Month and sex wise incidence of malaria infection in Zhob district

and P. falciparum were observed among different localities having different hygienic conditions.

In Zhob district (Table 1-4), the over all incidence of Plasmodium slide positivity was 41.8% (3240/7748), wherein P. vivax was observed to be highest (51.8%: 1681/3240) as compared with that of P. falciparum (48.1%: 1559/3240). Among children of the age group 1-10 years, P. vivax was observed higher (52.8%:644/1219) than P. falciparum (47.1%: 575/1219). Similarly, in the age group of 11-20 years, P. vivax was found more (52.8%: 553/1047) than P. falciparum (47.1%:494/1047). Whereas in the age group of 21 years and above, P. falciparum was found higher (50.3%:490/974) than P. vivax (49.6% (484/974). Seasonal variation was also noted. The highest infection of P. vivax (85.4%:141/165) was noted in March and lowest 18.6%:59/316) in October while P. falciparum was highest (81.3%: 257/316) in October and lowest (14.5%: 24/165) in March. Sex wise ratio was also noted. Male to female ratio was 3.4:1 (2514:726).

Table 1-4 were statistically analyzed to test whether there is any association between types of infection and age groups through χ² at 5% level of significance, χ² calculated as 2.67791 (Table 3B) and compared with the table value of χ² = 5.991. Since calculated value of χ² is less than the table value so it is concluded that there is no association between types of infection and age groups.

Malaria affects an estimated 300 million people and causes more than a million deaths per year worldwide. Falciparum malaria has high mortality as it causes complications like cerebral malaria, renal failure and algid malaria (Bhalli and Samiullah, 2001).

In present study, the incidence of P. vivax was observed to be higher (51.8%: 1681/3240) as compared with that of P. falciparum (48.1%: 1559/3240). Similarly, Yar et al. (1998) while studying prevalence of malarial parasite species in Multan district, observed high incidence of P. vivax (60.5%) and a low incidence of P. falciparum (37.2%) with slide positivity rate 17.2%. Similarly, Jan and Kiani (2001) while studying malarial parasites in Kashmiri refugees settled in Muzaffarabad reported high incidence (6.3%) of P. vivax than of P. falciparum (0.6%) with slide positivity rate 7%. Mohammad and Hussain (2003) observed high incidence of P. vivax (5.7%) and 1% P. falciparum infection among the general population of district Buner. Sheikh et al. (2005) reported high rate of P. vivax (66.8%: 61313/91679) than P. falciparum (30.7%: 28166/91679). Jalaluddin et al. (2006) studied 160 cases of children at a private clinic in Mansehra (NWFP) and found slide positivity rate 96.2% and P. vivax was noted to be higher (92.2%) than P. falciparum (7.7%). In Iran south east of Caspian sea, Zarchi et al. (2006) observed slide positivity rate 9.6% and P. vivax was found higher (61%) than P. falciparum (20.7%). Idris et al. (2007) investigated malaria infection at Ayub Teaching Hospital Abbottabad and observed slide positivity rate 7.2% and P. vivax was found higher (72.4%) than P. falciparum (24.1%). Similarly, Yasinzai and Kakarsulemankhel (2007) studied incidence of malaria infection in central areas of Balochistan (Mastung and Khuzdar) and found over all slide positivity rate 26.6% and P. vivax was observed higher (62.5%) than P. falciparum (37.4%).

However, mixed infection of P. vivax and P. falciparum was not observed in the present study, as mixed infection of 2.3% was observed in Multan district by Yar et al. (1998). Zarchi et al. (2006) and Idris et al. (2007) also observed mixed infection 18.3 and 3.4%, respectively in Iran and Abbottabad. During present study, P. malariae and P. ovale infection was not seen in any patient as the same was also not observed by Yar et al. (1998) in Multan and Idris et al. (2007) in Abbottabad. High rate of P. vivax (51.8%:1681/3240) was not only observed in our study, but observed in previous above mentioned studies also really poses an alarming health hazard in the country as it may lead to cerebral malaria as it was pointed out by Abbasi and Shaikh (1997) that recently World Health Organization has reported the occurrence of cerebral malaria also due to the P. vivax.

In spite of malaria control program, it still remains a great challenge. Keeping in view the results of the present investigation, Directorate of Malaria Control Program (MCP) Balochistan, should effectively arrange malaria control program. A joint effort in this regard is to be organized by Health Department, Irrigation Department and Local Government to eradicate the favorable epidemiological factors, which promote the spread of malaria, so as to ensure the public health of the inhabitants of mentioned areas.

This study has received financial support from the Higher Education Commission, Islamabad (Pakistan) through Balochistan University, under promotion of research, which is gratefully acknowledged.