A review of visceral leishmaniasis during the conflict in South Sudan and the consequences for East African countries

Abstract

Background: Visceral leishmaniasis (VL), caused predominantly by Leishmania donovani and transmitted by both Phlebotomus orientalis and Phlebotomus martini, is highly endemic in East Africa where approximately 30 thousands VL cases are reported annually. The largest numbers of cases are found in Sudan - where Phlebotomus orientalis proliferate in Acacia forests especially on Sudan's eastern border with Ethiopia, followed by South Sudan, Ethiopia, Somalia, Kenya and Uganda. Long-standing civil war and unrest is a dominant determinant of VL in East African countries. Here we attempt to identify the correlation between VL epidemics and civil unrest.

Objective and methodology: In this review, literature published between 1955 and 2016 have been gathered from MSF, UNICEF, OCHA, UNHCR, PubMed and Google Scholar to analyse the correlation between conflict and human suffering from VL, which is especially apparent in South Sudan.

Findings: Waves of forced migration as a consequence of civil wars between 1983 and 2005 have resulted in massive and lethal epidemics in southern Sudan. Following a comprehensive peace agreement, but especially with increased allocation of resources for disease treatment and prevention in 2011, cases of VL declined reaching the lowest levels after South Sudan declared independence. However, in the latest epidemic that began in 2014 after the onset of a civil war in South Sudan, more than 1.5 million displaced refugees have migrated internally to states highly endemic for VL, while 800,000 have fled to neighboring countries.

Conclusion: We find a strong relationship between civil unrest and VL epidemics which tend to occur among immunologically naïve migrants entering VL-endemic areas and when Leishmania-infected individuals migrate to new areas and establish additional foci of disease. Further complicating factors in East Africa's VL epidemics include severe lack of access to diagnosis and treatment, HIV/AIDS co-infection, food insecurity and malnutrition. Moreover, cases of post-kala-azar dermal leishmaniasis (PKDL) can serve as important reservoirs of anthroponotic Leishmania parasites.

Keywords: Civil war; Conflict zone; East Africa; Leishmania donovani; Phlebotomus orientalis; Refugees; South Sudan; Visceral leishmaniasis.

Fig. 1

Distribution of visceral leishmaniasis (VL) cases in East Africa. a This satellite image is taken from Google Maps. b The distribution of VL for each region or state within East African countries [5, 27, 35, 36]. The largest affected area in terms of number of cases is the eastern region of Sudan and neighboring Ethiopia (Area 1), followed by South Sudan (Area 2), Darfur and Western Sudan (Area 3), and Somalia (Area 4), and Kenya with North East Uganda (Area 5)

Fig. 2

Timeline of political unrest and number of VL deaths and cases in South Sudan [, –41]. Between 1983 and 2005 VL claimed approximately 100,000 lives in Southern Sudan. During this time there was also an on-going civil war in Sudan. In 2005 a Comprehensive Peace Agreement was signed. Between 2005 and 2008 an estimated 7,400 to 14,200 VL cases were reported annually in South Sudan. In 2011, South Sudan gained independence from Sudan and VL cases declined sharply to fewer than 5,000 cases in 2012 and to the lowest level in 2013 when only 2,714 cases were reported in South Sudan. In 2013 the nation of South Sudan entered into a civil war and experienced a doubling of the number of cases of VL cases in Lankien, Jonglei State and Malakal in Upper Nile State in 2014 with more than 6,700 cases treated. The exact number of cases between 1983 and 2005 is unknown, but must have been well over 100,000

Fig. 3

The “perfect storm” of conditions leading to VL Epidemics [, –47]. The overarching problem in South Sudan since 2013 has two major factors. The first is a large population of naïve individuals migrating to endemic regions. In this case, migrations usually occur due to civil unrest leading to the second factor: a breakdown in infrastructure. This breakdown has led to lack of adequate shelter, food insecurity and collapsed healthcare systems, which leave individuals highly vulnerable to exposure to phlebotomine sand flies

Fig. 4

Number of refugees displaced internally or to neighbouring East African countries between 2014 and 2015 [–, , , , , –55]. The number of refugees in East African nations of Sudan, Eritrea, Djibouti, Somalia, Ethiopia, Kenya, Uganda and the states of South Sudan are shown. Numbers range from 0 to less than 50,000 to over 600,000 and are represented by intensity of color on the map

Fig. 5

Consequences of conflict on South Sudan and neighbouring countries [44, 56]. This timeline represents the human toll of the recent political unrest in South Sudan and neighbouring countries. Consequences include not only forced displacement, but also outbreaks of VL due to the factors listed in Fig. 3