Saturday, July 29, 2017

Ethiopia 2017 - Day 11. Addis Ababa

Not much to report. Getachew and I met for another brainstorming session, which took a side turn and we ended talking about how much good work has been done in Ethiopia, and how it is important that the international community learns about it. I was loaded with brochures, a DVD, and a very handsome set of posters, and Getachew anointed me as ambassador plenipotentiary to the administration of CSU Stanislaus. At a minimum I am to show slides of this beautiful country, and convey to anyone who will listen to me a warm invitation to come visit Ethiopia.

Let me make a pause in this narrative (but I promise it is relevant to Ethiopia, as you will see later) to talk about thoughts I have had about my trip to Ghana in just four-days time. I was reflecting that Ghana is currently enforcing the Yellow Fever vaccine, so I presume they are engaged in a campaign to eradicate this disease. Realizing that I know very little about this I immersed myself in some internet research, which in turn led me to malaria and encephalitis, and coming around in full circle to sleeping sickness in Ethiopia. Here is what I have learnt:

Yellow Fever was a mysterious and deadly disease as early as the late 1800’s and early 1900’s. At the time it was believed to be associated with filth, and to be transmitted by contact with the dirty linen, vomit, blood and other unmentionable fluids of infected patients. The first breakthrough came when, in investigating malaria, a doctor dissected an Anopheles female mosquito and found the same protozoan that was found in the blood of malaria patients. Later observations indicated that Anopheles was the only mosquito that did this, so the best preventive measure to control the disease was to control the mosquito. Easier said than done, because Anopheles, a comparatively large, brown mosquito with tiny black dots in its wings, is ubiquitous in both urban and rural environments.

Enter now Stegomaya fasciata, a comparatively small, silvery mosquito which appears to be the vector for yellow fever. But it was a difficult, tenuous connection to establish, partly because this is a viral disease where the microscope cannot detect the culprit. The mosquito had been seen feeding in Yellow Fever patients, but when that same mosquito was allowed to sting healthy volunteers over the next couple of days nothing happened. Besides, relatives could visit someone recently affected by the disease without consequences, but after two weeks everyone who came to visit was thunderstruck by the yellow jack. The last piece of information was that once a patient had died, volunteers sleeping on the soiled linen of the deceased were not affected. So late 1800’s physicians came up with the wild concept of ex-incubation. Under this scenario an individual would be stung by a Stegomaya female, but it would take two or three days for that individual to become infectious. After that couple of days another Stegomaya would sting and suck infected blood, but then the infectious agent (now we know it is a virus) would have to incubate in the body of the mosquito for a couple of weeks before it became active and was ready to infect new victims. The key, then, was to prevent the mosquito from reproducing by limiting its access to stagnant water, where the female deposits its eggs. The first proof of concept came when the Chief Medical Officer of the American forces occupying Habana had to tackle the high yellow fever mortality among the troops. The mosquito hypothesis had been newly minted, and Dr. Gorgos was not ready to believe it, but for lack of anything better he instituted a house-to-house search and inspection to cover the tinajas where drinking water was kept, drain puddles and other open sources of water, and spread oil over stagnant waters. The results were miraculous. In six months the number of cases had dropped to a tenth of what they had been the previous years, and within a year the rate had dropped to zero cases! Interestingly malaria cases also had dropped significantly, but not to zero (A matter of the reproduction of Anopheles being impeded at the same time, but not to the same extent, than that of Stegomaya. The latter is a bit like rats, only found around human settlements, whereas Anopheles is also a country dweller). Incidentally, Stegomaya is now called Aedes aegypti.

Note: An alternate mode of control, for both malaria and yellow fever, is to have a healthy population, so even if there are mosquitoes around they cannot get infected and pass over the disease. I suspect that this is what Ghana is striving for.

OK, back to Ethiopia and my friend Getachew. The silent killer here is sleeping sickness, which can strike both humans and cattle. The agent is the protozoan Trypanosoma brucei, and the vector is the tse tse fly, Glossina sp. The reservoirs are infected people, pigs, cattle, and some game animals. It is a nasty disease that is endemic to sub-Saharan Africa, which can persist as a chronic disease for years, or follow an acute path that can lead to death. Currently there are few preventive measures (e.g., no effective immunization vaccine has been developed), so the key measure is vector control (pesticides, nets, or ???). This is where Getachew has made a significant contribution; he devised a tse-tse trap using a small blue tarp, an old plastic coke bottle, and a bowlful of cow urine. The whole contraption looks like a tepee constructed with the tarp, with the urine bowl in the center, and the plastic bottle on top, like if it were smoke coming out of the tepee. The fly gets attracted by the smell of the urine, flies up inside the blue tepee seeking the light, enters the bottle, and gets cooked by solar radiation inside the bottle. Beautifully simple but very effective!

By now you are probably tired of hearing about exotic diseases, but they are very much alive within Africa, and controlling them needs to be a high priority in sub-tropical regions.

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