New publication: Environmental and Household-Based Spatial Risks for Tungiasis in an Endemic Area of Coastal Kenya
New publication! I started working on this cool project on tungiasis (jiggers) with colleagues in Kenya and Japan way back in 2014. Today, I am happy to say that after much ado our work has finally seen the light of day, thanks to Nagasaki PhD student (and soon to be Dr.) Ayako Hyuga. It appears today in the journal Tropical Medicine and Infectious Disease (MDPI).
Environmental and Household-Based Spatial Risks for Tungiasis in an Endemic Area of Coastal Kenya
“#Tungiasis is a #cutaneous #parasitosis caused by an embedded female sand flea. The distribution of cases can be spatially heterogeneous even in areas with similar risk profiles. This study assesses household and remotely sensed environmental factors that contribute to the geographic distribution of tungiasis cases in a rural area along the Southern Kenyan Coast. Data on household tungiasis case status, demographic and socioeconomic information, and geographic locations were recorded during regular survey activities of the Health and Demographic Surveillance System, mainly during 2011. Data were joined with other spatial data sources using latitude/longitude coordinates. Generalized additive models were used to predict and visualize spatial risks for tungiasis. The household-level prevalence of tungiasis was 3.4% (272/7925). There was a 1.1% (461/41,135) prevalence of infection among all participants. A significant spatial variability was observed in the unadjusted model (p-value < 0.001). The number of children per household, earthen floor, organic roof, elevation, aluminum content in the soil, and distance to the nearest animal reserve attenuated the odds ratios and partially explained the spatial variation of tungiasis. Spatial heterogeneity in tungiasis risk remained even after a factor adjustment. This suggests that there are possible unmeasured factors associated with the complex ecology of sand fleas that may contribute to the disease’s uneven distribution.” #environmental #kenya #NTD #NeglectedTropicalDisease #parasitology #globalhealth #publichealth
Its always a thing to celebrate, getting these new papers out. This one covers a topic close to home. After years of doing global health work, I never thought I’d be doing domestic health and even less certain that I’d be covering topics just down the road from me.
Together with partners from Wayne State University (Health Urban Waters), UM-Dearborn and the University of Michigan Ann Arbor, we characterized the state of recurrent flooding in Detroit, MI and explore possible public health impacts. The article appears in the International Journal of Environmental Research in Public Health. This was extremely rewarding work.
Article is open access.
Household flooding has wide ranging social, economic and public health impacts particularly for people in resource poor communities. The determinants and public health outcomes of recurrent home flooding in urban contexts, however, are not well understood. A household survey was used to assess neighborhood and household level determinants of recurrent home flooding in Detroit, MI. Survey activities were conducted from 2012 to 2020. Researchers collected information on past flooding, housing conditions and public health outcomes. Using the locations of homes, a “hot spot” analysis of flooding was performed to find areas of high and low risk. Survey data were linked to environmental and neighborhood data and associations were tested using regression methods. 4803 households participated in the survey. Flooding information was available for 3842 homes. Among these, 2085 (54.26%) reported experiencing pluvial flooding. Rental occupied units were more likely to report flooding than owner occupied homes (Odd ratio (OR) 1.72 [95% Confidence interval (CI) 1.49, 1.98]). Housing conditions such as poor roof quality and cracks in basement walls influenced home flooding risk. Homes located in census tracts with increased percentages of owner occupied units (vs. rentals) had a lower odds of flooding (OR 0.92 [95% (CI) 0.86, 0.98]). Household factors were found the be more predictive of flooding than neighborhood factors in both univariate and multivariate analyses. Flooding and housing conditions associated with home flooding were associated with asthma cases. Recurrent home flooding is far more prevalent than previously thought. Programs that support recovery and which focus on home improvement to prevent flooding, particularly by landlords, might benefit the public health. These results draw awareness and urgency to problems of urban flooding and public health in other areas of the country confronting the compounding challenges of aging infrastructure, disinvestment and climate change.
Are dogs associated with infections by a skin burrowing flea in Kenya? Masanobu Ono and I with Kensuke Goto, Satoshi Kaneko, mwatasa Changoma just published a paper on #tungiasis in the journal Tropical Medicine and Health.
Most people haven’t heard of tungiasis, an ectopic skin disease caused by the skin burrowing parasite, T. pentrans. It causes itching, pain, is associated with serious secondary bacterial infections, gangrene, social exclusion and debilitation. It primarily afflicts the very young and very old and is found almost exclusively in the poorest parts of the poorest parts of the world. It fits the classic definition of a neglected tropical disease.
We explored associations of wildlife and domesticated animals with household level tungiasis in Kenya using a two stage complex sampling based survey in an area adjacent to a wildlife preserve.
Tungiasis is a ectopic skin disease caused by some species of fleas in the Tunga genus, most notably T. penetrans. The disease afflicts poor and marginalized communities in developing countries. Transmission of tungiasis comprises a complex web of factors including domesticated animals and wildlife. This research explores animal and environmental risk factors for tungiasis in an area adjacent to a wildlife reserve in Kwale, Kenya.
A two-stage complex sampling strategy was used. Households were selected from three areas in and around Kwale Town, Kenya, an area close to the Kenyan Coast. Households were listed as positive if at least one member had tungiasis. Each household was administered a questionnaire regarding tungiasis behaviors, domesticated animal assets, and wild animal species that frequent the peridomiciliary area. Associations of household tungiasis were tests with household and environmental variables using regression methods.
The study included 319 households. Of these, 41 (12.85%) were found to have at least one person who had signs of tungiasis. There were 295 (92.48%) households that possessed at least one species of domesticated animal. It was reported that wildlife regularly come into the vicinity of the home 90.59% of households. Presence of dogs around the home (OR 3.85; 95% CI 1.84; 8.11) and proximity to the park were associated with increased risk for tungiasis infestation in humans in a multivariate regression model.
Human tungiasis is a complex disease associated with domesticated and wild animals. Canines in particular appear to be important determinants of household level risk.
Currently, I am a part of a project looking at climate change impacts on the distribution of tree and grass pollens in the US and associations with allergy and asthma related emergency room visits
As part of that, we are collecting baseline data on symptomatic profiles of patients who are sensitive to tree and grass pollens and are currently undergoing immunotherapy in local clinics.
Our survey is two fold, the first a baseline survey of types of demographics, types of allergies, seasonal sensitivities, general symptoms and lifestyle impacts, the second a three week survey of sleep quality and allergy and asthma related events.
We hope to gather data to see how the ragweed season might impact general health and well being using a coarse raster of predicted pollen distribution.
The survey is being conducted at the University of Michigan Allergy Specialty Clinic and Food Allergy Clinic at Domino’s Farms and will include approximately 50 people.
At least that’s what we hope happens. Yesterday, I had the opportunity to join the Detroit Communities Reducing Energy and Water (use) project, focusing on Parkside, a subsidized housing community in Detroit, MI.
The project aims to help residents make changes to the electrical and plumbing infrastructure of their homes to reduce the energy costs. Residents in poor communities often live in housing that has old, inefficient and sometimes faulty electrical wiring, kitchen appliances and aging or damaged pipes, showers and toilets.
The University of Michigan School of Public Health has a community based participatory research project with the residents of Parkside, the Friends of Parkside, a local advocacy group.
We administered a survey on energy, housing conditions and health to about twenty residents who came to the event. Following the consumption of copious amounts of pizza, the goals of the study were explained to everyone in a group meeting and consent was obtained.
They then moved to another room and took the survey. Many of the residents were elderly, mostly women. All had interesting stories to tell about broken air conditioners, unresponsive maintenance crews, family, friends, kids…. everything you find in these kinds of surveys.
After they were done, they all got some ca$h and were provided with a temperature monitor so that we can better understand what they are experiencing in their homes during these hot summer months. We will then conduct a follow up survey to assess the impact of a home based educational program on energy use and health.
It had been a long time since I was involved in community and I was grateful to be a part of. Some people don’t like this kind of work, I really don’t understand what’s not to like about hanging out with survey respondents who feel invested in the project and their communities.
Humans have had to deal with the threat of snakebites as long as humans have existed. While deaths from snakebites are rare, the outcomes are so severe and the nature of the animal so mysterious, that humans have developed all sorts of ways of dealing with them.
Witchdoctors, or Mganga as they are known in East Africa, are the first line for snakebite treatment here. The Waganga are fairly useless for treating many serious health issues, but they have carved out a niche for themselves for a few public health problems.
Our survey in Western Kenya confirms that nearly 100% of people who have been bitten by a snake visit the Mganga, regardless of whether they visit a formal health facility or not.
I went and sat down with an established Mganga here in Kwale and he was gracious enough to answer all of my questions openly and (mostly) honestly.
Hello, thank you for taking the time to speak with me today. Is English OK?
No, my English is not very good. Can we do this through a translator?
Of course. So, what happens when a patient comes in for treatment for a snakebite?
When the patient comes in, I first apply the “njiwe na njoka” (lit: snake stone). The stone sucks all the poison out of the wound. When you put it on the bite, it will stick. When the stone has absorbed all the poison, it will fall off.
What do you mean? Like it just sticks to the flesh without tying it?
Yes, if there is poison, the stone will stick to the body. When all the poison is gone, the stone will fall off. After it is done, I take the stone and wash it with milk several times and then use it again for the next patient.
What is the snake stone? Is it like a rock? I’ve seen people use charcoal in the villages. They tie it to the wound, it doesn’t appear to stick on its own.
No, this is different. This is a stone from the snake. The stone is in the skull of the snake, like that of a fish.
(Note: I did not know this, but some species of snakes have otoliths, like most fish. Snakes (and fish) are deaf in the traditional sense. The otolith is a piece of calcium which grows as the animal ages and sit on top of a bed of nerves. When there are vibrations, the otolith vibrates, stimulating the nerve bed so that the animal can “hear” motion around it. Not all snakes have otoliths but some species of burrowing snakes do.)
Where do you get the stone? Can you just buy it in the market?
The snake stones come from the Maasai, from big snakes in Maasai land. My teacher travels to Maasai land to get them and brings them back.
If the wound is fresh, I apply the stone. However, if it has been two or three days since the bite, I can’t use the stone anymore. Then I have to use a special medicine made from herbs and crushed snake heads. I mix it all together, then crush it into a powder and keep in a gourd.
When the patient comes in, I use a new razor blade to make small scratches on the wound. Then I rub the powder in it and bandage the wound. The wound will try to heal over time, so you have to make the scratches to be able to apply the powder.
Do you use the razor blade again?
No, I always use a new blade. (He was emphatic on this point.)
What is the powder made from?
Snakeheads. When we kill a snake, we keep the heads to make the powder. We mix it with roots, bark and leaves from special plants from deep in the forest. My teacher is a security guard in one of the forests and can get them when he can find them.
Wait, so your teacher is a forest ranger? Can’t he get by being an Mganga?
Yes. He is a forest ranger.
So he took the job so that he can get the plants from the forest whenever he needs them.
OK, so how many bites do you see per month?
It depends, some months I get more than others but mostly one every three months or so.
Do you refer them to the health facility for formal treatment?
Yes, I do. I treat them, then they go to the facility, then they come back to me. (I’m suspicious on this point, though the Mganga in question appears more together than most.)
Is there a religious component to this?
Well, there are two kinds of bites, those where the snake just bites and there is no witchcraft and those where someone has used magic to send the snake to bite you.
How do you know the difference?
If the bite heals quickly, there is no witchcraft. But if the bite is treated and does not improve then there is definitely witchcraft involved. At that time, I have to use powerful magic to get rid of the curse.
What do you do?
I send the snake back to the person who applied the curse. When we hear that someone nearby has been bitten, we know who applied the curse.
(Note: this is not uncommon. Witchcraft is often associated with hatred and revenge but the person applying the curse risks becoming cursed themselves. It is possible that snakebites are seen as a never ending battle of malevolent spiritual forces. What this does is sow distrust among people, even families and the Mganga is seen as the only cure. The result is that the Mganga are never without work.)
How did you learn this craft?
I was sick for a long time with stomach and head problems. I went to the hospital and it never got better so then I went to an Mganga. I improved. The Mganga suggested that I become on and I started training under him.
Thank you very much for your time.
We just spent the day driving around Kwale looking for snakes, and/or people who had been bitten by snakes. As the last post showed, snakebites are a persistent problem along the Kenyan Coast, with more then 5% of the households we survey indicating that at least one person in the household had been bitten in the past two years.
It wasn’t difficult to find them.
Snakes are universally feared all over Africa and the associations with witchcraft make it a common topic of discussion. Everyone knows someone who has been bitten. They often know all the details, including where it happened and what occurred following the bite. It’s never a happy story.
We went deep into Kinango, an extremely rural area west of Kwale Town and found a friendly lady who seemed to know everything about everyone. She was incredibly jolly, pulled out some plastic chairs for us to sit under and cracked jokes the whole time. I even got to copy her collection of Sangeya music which she had recorded on her phone (another post but you can hear some of it here) at some local music festivals. In total I got more than five hours of live Sengeya and Chilewa music. In the music world, these would be called “field recordings.” Here, this is just music she cooks and cleans to.
Switching back and forth between snakes and Sengenya (in Africa it seems to be possible to have multiple conversations at once), she told us about a kid who had been bitten two days previous. She even told us where to find her, so off we went.
The child was collecting firewood around a mango tree near her home, when she was suddenly bitten by a large green snake, not once but three times on the foot. The snake bit once skated away, decided it wasn’t enough and came back and bit her twice more.
Ants had moved into the dead tree and hollowed out the area underneath. Presumably, the snake moved in previously and came out to warm up during the day.
The mother thankfully took the child immediately to Kinango Hospital and treated was administered. The child was given a three day course of antivenom injections and charcoal was wrapped around the wounds to absorb any venomous discharge. Though the child complains of some numbness in the area, it looks as if there won’t be any permanent damage. Thankfully.
We were also told of an old woman who had been bitten more than 20 years ago, and was badly scarred, figured out where she was and off we went again.
As we pulled up a friendly young lady came out to greet us, and showed us the way to the house out back. In the distance, we could see an old lady walking with a limp. Otherwise, she was completely fit and seemed to be cutting her own firewood with a panga.
She brought us out some chairs and sat down to chat. In 1992, she had been out back collecting firewood (a pattern) and was bitten on the foot by puff adder, one of the deadliest snakes in the world. She was bitten on the foot, and became immobile for nearly a week. A series of witch doctors were brought in, who administered charcoal rubbed into small cuts in the skin.
Necrosis set in, and watery blood erupted out of the wound site. A large number of maggots appeared. Finally, someone had the good sense to take her to the hospital, where she spent an entire year.
The details were unclear, but it appeared that the gangrene was so severe that multiple infections were presents. They likely had her on intravenous antibiotics for an extended amount of time. Despite this, the foot did not heal. Some Christian missionaries came, and convinced her to convert to Christianity, which, she claimed, improved her condition. This is likely coincidental.
The doctors suggested a skin graft to improve the foot, but she refused. Necrosis was so deep that it permeated the bone and the foot is permanently curved as a result. The leg still shows sign of swelling even more than 24 years after the bite. In most cases, they probably would have simply amputated.
The lady was born in 1948, bore ten children, one of which was born just as she was bitten. She was unable to breast feed or care for the child. Regardless, the daughter has two children of her own now.
Snakebites are bad news. In this woman’s case, the disregard for proper medical care simply made a bad situation worse. She is truly lucky to be alive. If she had died, it is doubtful that the Mgangas would have admitted any responsibility.
Doing research in developing countries is not easy. However, with a bit of care and planning, one can do quality work which can have an impact on how much we know about the public health in poor countries and provide quality data where data is sadly scarce.
The root of a survey, however, is sampling. A good sample does its best to successfully represent a population of interest and can at least qualify all of the ways in which it does not. A bad sample either 1) does not represent the population (bias) and no way to account for it or 2) has no idea what it represents.
Without being a hater, my least favorite study design is the “school based survey.” Researchers like this design for a number of reasons.
First, it is logistically simple to conduct. If one is interested in kids, it helps to have a large number of them in one place. Visiting households individually is time consuming, expensive and one only has a small window of opportunity to catch kids at home since they are probably at school!
Second, since the time required to conduct a school based survey is short, researchers aren’t required to make extensive time commitments in developing countries. They can simply helicopter in for a couple of days and run away to the safety of wherever. Also, there is no need to manage large teams of survey workers over the long term. Data can be collected within a few days under the supervision of foreign researchers.
Third, school based surveys don’t require teams to lug around large diagnostic or sampling supplies (e.g. coolers for serum samples).
However, from a sampling perspective, assuming that one wishes to say something about the greater community, the “school based survey” is a TERRIBLE design.
The biases should be obvious. Schools tend to concentrate students which are similar to one another. Students are of similar socio-economic backgrounds, ethnicity or religion. Given the fee based structure of most schools in most African countries, sampling from schools will necessarily exclude the absolute poorest of the poor. Moreover, if one does not go out of the way to select more privileged private schools, one will exclude the wealthy, an important control if one wants to draw conclusions about socio-economic status and health.
Further, schools based surveys are terrible for studies of health since the sickest kids won’t attend school. School based surveys are biased in favor of healthy children.
So, after this long intro (assuming anyone has read this far) how does this work in practice?
I have a full dataset of socio-econonomic indicators for approximately 17,000 households in an area of western Kenya. We collect information on basic household assets such as possession of TVs, cars, radios and type of house construction (a la DHS). I boiled these down into a single continuous measure, where each households gets a wealth “score” so that we can compare one or more households to others in the community ( a la Filmer & Pritchett).
We also have a data set of school based samples from a malaria survey which comprises ~800 primary school kids. I compared the SES scores for the school based survey to the entire data set to see if the distribution of wealth for the school based sample compared with the distribution of wealth for the entire community. If they are the same, we have no problems of socio-economic bias.
We can see, however, from the above plot that the distributions differ. The distribution of SES scores for the school based survey is far more bottom heavy than that of the great community; the school based survey excludes wealthier households. The mean wealth score for the school based survey is well under that of the community as a whole (-.025 vs. -.004, t=-19.32, p<.0001).
Just from this, we can see that the school based survey is likely NOT representative of the community and that the school based sample is far more homogeneous than the community from which the kids are drawn.
Researchers find working with continuous measure of SES unwieldy and difficult to present. To solve this problem, they will often place households into socio-economic "classes" by dividing the data set up into . quantiles. These will represent households which range from "ultra poor" to "wealthy." A problem with samples is that these classifications may not be the same over the range of samples, and only some of them will accurately reflect the true population level classification.
In this case, when looking at a table of how these classes correspond to one another, we find the following:
Assuming that these SES “classes” are at all meaningful (another discussion) We can see that for all but the wealthiest households more than 80% of households have been misclassified! Further, due to the sensitivity of the method (multiple correspondence analysis) used to create the composite, 17 of households classified as “ultra poor” in the full survey have suddenly become “wealthy.”
Now, whether these misclassifications impact the results of the study remains to be seen. It may be that they do not. It also may be the case that investigators may not be interested in drawing conclusions about the community and may only want to say something about children who attend particular types of schools (though this distinction is often vague in practice). Regardless, sampling matters. A properly designed survey can improve data quality vastly.