Podoconiosis, a neglected lymphatic tropical disease

Podoconiosis causes a painful massive swelling of the lower limbs, bilaterally and asymmetrically. It is caused by exposure to particles common in soils of volcanic origin and is second only to lymphatic filariasis as the leading cause of tropical lymphoedema. An estimated 4 million people live with podoconiosis globally in 32 potentially endemic countries. Podoconiosis is associated with positive family history of podoconiosis, bare foot, gender, poor housing condition, foot hygiene, income and educational status of the affected patients. There are also cultural barriers involved in maintaining a high epidemiology of the disease. Podoconiosis was never been prioritized either in intervention or research programmes. This may be due to the lack of resources for new health initiatives, which is a common problem in the low-income tropical countries in which this disease is present. Only Ethiopia, Cameroon, and Rwanda report podoconiosis within their routine health management information systems.We believe that comprehensive podoconiosis control strategies such as promotion of footwear and personal hygiene are urgently needed in endemic countries in the African Region. Mapping, active surveillance and a systematic approach to the monitoring of disease burden must accompany the implementation of podoconiosis control activities. Definition and epidemiology Until 20 years ago, podoconiosis was practically not described in medical literature, and the sufferers was a private matter that was not dealt with by the formal heath sector.1 Podoconiosis causes a painful massive swelling of the lower limbs, bilaterally and asymmetrically. It is caused by exposure to particles common in soils of volcanic origin and is second only to lymphatic filariasis as the leading cause of tropical lymphoedema. An estimated 4 million people live with podoconiosis globally in 32 potentially endemic countries.2 Podoconiosis is found in highland areas of tropical Africa, Central America and north-west India. In Figure 1 it well apparent the global distribution of podoconiosis.3 Despite the significance of the disease, its global distribution and epidemiology are poorly understood, according to WHO document where is reported that in many endemic countries prevalence and incidence were never investigated.2 A systematic review assessed the epidemiology of podoconiosis in 18 endemic coutries from Africa, 3 from Asia and 11 from Latin America. None of the Latin American countries reported prevalence data, although some countries are suspected to be endemic.3 In 2011 the World Health Organization (WHO) recognized podoconiosis as one of the neglected tropical diseases (NTDs) under the category of ‘other tropical conditions’.2 Subsequently Ethiopia, Rwanda and Cameroon recognized podoconiosis as a priority NTD and included it in their longterm health plans, with scarce results, yet. The peculiarity of podoconiosis Podoconiosis is really a different disease respect to lymphedema in the Western Countries or to lymphatic filariasis in the tropical regions. Podoconiosis is caused by exposure to red clay soil, and results from a classic interaction between genes and environmental factors. Particularly, mineral particles from the soil penetrate the skin and are taken up by macrophages in the lymphatic system which causes inflammation and fibrosis of the vessel lumen leading to blockage of the lymphatic drainage. This results in oedematous feet and legs and subsequently progresses to elephantiasis and fibrous-edema. These changes are themselves disabling, and painful intermittent acute lymphangitis episodes cause further aggravation (Figure 2).4 There is lack of knowledge regarding the pathogenesis of the disease because it is still unclear why podoconiosis strikes not all the people who does not foot wear in the endemic areas. Podoconiosis was associated with positive family history of podoconiosis, bare foot, gender, poor housing condition, foot hygiene, income and educational status of the affected patients.5 Individuals with family history of podoconiosis were 2.81 times more likely to develop podoconiosis than individuals with no family history of podoconiosis [AOR, 2.81 (95% CI: 1.7-4.64)]. This finding suggests the presence of unknown susceptibility genes. The probability of podoconiosis in barefooted individuals was 3.26 times higher than in individuals who wear shoe in their daily activities [AOR, 3.26 (95% CI: 2.035.25)]. This finding supports that barefooted patients individuals may allow soil substances to enter into their body, initiating the pathophysiology of the disease. The likelihood of the disease was found 3.85 times higher in the male gender, maybe due to different exposure distribution (working activities?). The risk of acquiring podoconiosis in people living in poor housing conditions was 83% higher [AOR, 0.17 (95% CI: 0.10.3)], supporting the role of personal hygiene. In fact the probability of the diseases in an individual who did not frequently keep his/her foot hygiene was 2.68 times higher than with an individual that keep his/her foot hygiene in their daily life [AOR, 2.68 (95 CI: 1.72 4.19)]. A further confirm is the 88% increased risk of podoconiosis in patients with low income [AOR, 0.12 (95% CI: 0.07-0.22)]. Finally, as compared to the illiterate, the risk of podoconiosis was 98% lower with primary education [AOR, 0.02 (95% CI: 0.01-0.04)], 99% for secondary education [AOR, 0.01 (95% CI: 0.005-0.02)] while tertiary education decreased the risk up to 99.97% [AOR, 0.003 (95% CI: 0.0010.007)]. This finding supports that educational status increases awareness on foot hygiene. One more peculiarity of podoconiosis in the endemic countries is linked to significant Correspondence: Paolo Zamboni, Chair HUB Center for Venous and Lymphatic Diseases, Regione Emilia Romagna, Azienda Ospedaliera Universitaria di Ferrara, Ferrara, Italy. Tel.: +39.0532237694. E-mail: paolozamboni@icloud.com