Malaria Reemergence in Northern Afghanistan

Field investigations were conducted in Kundoz Province, an Afghan high-risk area, to determine factors responsible for the rapid reemergence of malaria in that country, where 3 million cases were estimated to have occurred during 2002. Results indicate the presence of nonrice-field–dependent Plasmodium falciparum and rice-field–associated P. vivax malaria.

fi sh were continuously reared and widely introduced (5,6). After 1980, chronic political instability resulted in the progressive breakdown of malaria control activities (2).
Although existing malaria control efforts have focused mainly on the Kabul area, little is known about the situation in the irrigated rice-growing high-risk areas of northeastern Afghanistan (7). During 1996-2001, from 202,767 to 395,581 malaria cases were reported annually, sharply increasing in 2002 and 2003 with 590,176 and 591,441 cases confi rmed, respectively (7), and 3 million cases estimated annually (8). Takhar and Kundoz Provinces were most affected (7). In late 2003, P. falciparum incidence ranged from 0.002% in Wardak to 31% in Takhar Province. The other malaria cases were attributable to P. vivax (7). Our aim was to analyze the current status, risk factors, and epidemiology of malaria in Kundoz Province, a previously underreported risk area.

The Study
Newly contracted (excluding all follow-up patients with P. vivax relapses) malaria cases were confi rmed by light microscopy, using standard Giemsa staining according to the World Health Organization (WHO) national malaria treatment and diagnosis guidelines (7)(8)(9), and were detected passively in febrile patients seeking treatment in the Provincial Malaria Center, Kundoz City, from January Hook Co., Gainesville, FL, USA) without an additional CO 2 generator and indoors by using an aspirator in the ricegrowing areas of Kundoz City, Kanam, Khanabad, Angor Bag, Alchira, Malaghi, and Jan Guzar. Light Traps were set in housing areas within a 5-km radius of rice fi elds, which are located in or close to towns, villages, and housing areas. Anopheline larval monitoring was carried out using the WHO-recommended Frisbee disk method (10)  Anopheline adult outdoor abundance peaked in late August, with the following percentage monthly means: May (1.2%), June (9.5%), July (18.6%), August (35.2%), September (26.8%), and October (8.7%). Anopheline larval monitoring yielded 54.7% A. hyrcanus (0-68 larvae per dip; mean 12.3), and 45.3% A. pulcherrimus (0-49 larvae per dip; mean 9.8). No A. superpictus or A. culicifacies larvae could be detected in rice fi eld samples. Anopheline larval abundance peaked in late July and early August with the following monthly means: May (0%), June (17.9%), July (32.3%), August (36.2%), September (12.8%), and October (0.8%).
The P. falciparum and P. vivax polymorphs VK 210 and VK 247 circumsporozoite protein (CSP) positivity rates in anopheline pools (5 females per species) trapped indoors and outdoors from 2004 through 2005 were detected by using the VecTest Malaria Panel Assay dipstick ELISA (Medical Analysis Systems, Inc., Camarillo, CA, USA) and are listed in the Table. The available data indicate that A. superpictus is the principal P. falciparum vector. Three A. pulcherrimus pools positive for P. falciparum CSP indicate that this species may be partly involved in P. falciparum malaria transmission. Plasmodium CSP positivity values were higher in indoor-trapped A. superpictus (2004: χ 2 = 4.9; df = 1; p = 0.025). Of P. vivax CSP-positive pools, 90.6% were VK 247-reactive, and 9.4% were reactive against both VK 247 and VK 210, indicating a similar P. vivax genospecies distribution pattern as reported previously from eastern Afghanistan (12).

Conclusions
Our results show that malaria quickly reemerged in rice-growing Kundoz Province of northeastern Afghanistan. This may be due to various factors: 1) introduction of P. falciparum and P. vivax malaria by returning refugees (13); 2) environmental changes caused by intensifi ed rice growing in close proximity to towns, villages, and housing areas and therefore within fl ight range of endemic anopheline vectors (3,5); 3) increased abundance and breeding of the local principal vectors of P. vivax malaria stemming from intensifi ed rice growing and irrigation systems that serve as preferred breeding sites for A. pulcherrimus and A. hyrcanus (3,5); and 4) absence of widespread biological and chemical vector control measures, including effective larviciding in fl ooded rice fi elds (8).
Habitat and breeding site preferences of malaria vectors may play a major role in the differing epidemiologies of local P. falciparum malaria and rice-fi eld-dependent, exophilic and endophilic P. vivax malaria. Possible reasons for the decline in annual malaria cases after 2002, especially in endophilic P. falciparum malaria not dependent on rice fi elds, may include the introduction of insecticidetreated bednets, increased indoor spraying, and improved treatment and health education (7,8), as well as inhibiting climatic conditions (e.g., the extraordinarily cold 2005 spring/summer season). Current P. vivax malaria incidence rates indicate that future control efforts should emphasize large-scale management of potential mosquito breeding sites in rice-growing areas, including biological or chemical larviciding or both. The effectiveness of personal protection from exophilic P. vivax malaria vectors such as A. hyrcanus may be enhanced by simultaneous use of skin repellents and insecticide-treated clothing (14,15). Dr Faulde is assistant professor of medical entomology and parasitology on the medical faculty, University of Bonn, Germany, and director and senior adviser in medical entomology/zoology of the Bundeswehr Medical Service. His research interests include modes of transmission, epidemiology of, and fi eld-based "Near-Real-Time" surveillance systems for arthropod-and rodentborne diseases.