39.3.1 Distinguishing podoconiosis from lymphatic filariasis
The outward appearance of legs and feet affected by podoconiosis and lymphatic filariasis is very similar – you can’t tell the difference just by looking. But there are some questions you can ask the patient that can help you to decide which diagnosis is most likely to be correct.
Where does the patient live?
If the patient lives more than about 1,200 metres above sea level, then the leg swelling is likely to be due to podoconiosis. This is because the mosquitoes that transmit lymphatic filariasis cannot survive above this altitude – it is too cold at night. If the patient has always lived in dega or woina dega areas, or does not live in zones where lymphatic filariasis is known to be prevalent, then you should diagnose the leg swelling as podoconiosis.
Where did the disease start and what body parts are affected?
If it started in the feet and both feet/legs are affected, then the diagnosis is likely to be podoconiosis. If the swelling began in the groin and spread downwards, if only one leg is affected (look back at Figure 37.21a), and/or the lymph nodes in the groin are enlarged – then the disease is likely to be lymphatic filariasis.
Can you suggest why it is important to distinguish between podoconiosis and lymphatic filariasis? (Think back to Study Session 37.)
Podoconiosis is not infectious (it is caused by soil particles), so patients don’t need drug treatment because there is no infectious agent to kill; there is no vector so their houses don’t need to be sprayed to kill mosquitoes (unless, of course, malaria is endemic in the area). Treating podoconiosis with the drugs used to treat lymphatic filariasis would be a waste of precious resources and would not cure the disease.
Malaria can be transmitted by mosquitoes in communities up to 2,000 metres above sea level. See Study Session 5 in Part 1 of this Module.