PRO/EAFR> Echinococcus granulosus – Kenya: neglected tropical disease outbreak


A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Wed 18 Oct 2023 10:18 EDT
Source: The Conversation [edited]

Echinococcus granulosus, a type of tapeworm, is a harmful parasite
that affects 1 million people worldwide. The parasite can grow slowly
in people for years to form thick-walled cysts in vital organs, such
as the liver and lungs. Known as cystic echinococcosis, or hydatid
disease, it can cause abdominal pain, nausea and vomiting. And if not
treated, it can be fatal.

It’s a zoonotic disease, meaning it spreads from animals to people,
with a life cycle involving humans, dogs and ruminant livestock. It’s
also considered a neglected disease by the World Health Organization
(WHO). It needs greater attention because of how dangerous it can be
and because treatment can be invasive and expensive. It costs US$3
billion a year globally to treat cases and compensate for losses to
the livestock industry.

In Kenya, the disease has long been endemic — meaning present over a
long period of time at a relatively low level — in pastoralist
communities who live and work closely with livestock, in northwestern
Kenya and Maasailand. Traditional pastoralist livestock farming in
Kenya’s north, for example in Turkana, has concentrated the risk of
disease in communities there. But populations in other parts of Kenya
are increasing, and thus so is the demand for meat. As a result, more
animals are being driven south for slaughter, bringing tapeworm
infections with them.

We’re part of a collaboration between the International Livestock
Research Institute, Jomo Kenyatta University of Science and
Technology, the University of Liverpool and the Kenya Medical Research
Institute. We’ve tracked the spread of Echinococcus tapeworm into
populations in a non-endemic area for the first time. This work is
important so that steps can be taken to prevent the spread of such
diseases, particularly from animals to humans.

We conducted 4 pieces of research which covered how prevalent
Echinococcus tapeworm was in livestock being brought for slaughter,
how it spread to people and how great the human disease burden was.
We’ve found that the parasite is highly prevalent in livestock moving
into these non-endemic areas and is now spreading, via dogs, into
human populations. Our findings highlight how important it is to carry
out disease surveillance, particularly as populations grow and
dynamics change.

Our studies focused on Busia and Bungoma counties, which border one
another and which previously didn’t have the tapeworm disease, cystic
echinococcosis, among humans and livestock. For our first study we
assessed how prevalent tapeworm was in livestock being brought for
slaughter. Over 2 years, we collected over 16 000 reports in both
counties and found a very high infection rate in the samples we
collected — 32% of the livers of cattle and goats, 74% of lungs in
cattle and 58% of lungs in goats.

Our second and third studies sought to understand how Echinococcus
tapeworm might spread to humans in the counties. We hypothesised that
local dogs could be acting as the vector. Dogs congregate at slaughter
facilities and consume whatever is discarded. For instance, we saw
that often lungs from slaughtered animals were being discarded because
of hydatid cysts. Dogs could get tapeworms from eating meat like

We tracked the movements of 73 dogs using GPS collars over 5 days each
and saw that they regularly visited slaughterhouses. Through examining
their faecal samples, we saw that the parasite was present, and 16%
were positive for Echinococcus antigens in faeces. This meant they
could bring the disease to households and people.

The parasite matures in the dogs’ intestines, and the dog sheds eggs
in faeces, contaminating the environment. People get infected when
inadvertently parasite eggs from the environment are eaten, usually
due to poor household hygiene.

Our final study was to examine how great the human disease burden was
in Bungoma county. Using ultrasound technology, we found cystic
lesions which may indicate Echinococcus infection among a small
number (around 1%) of the community members.

While we did not find the population extensively suffered from this
disease, we detected early signs of the establishment of a local
transmission cycle. This means that the parasite has been introduced
and is spreading slowly in groups of people and dogs which have not
been exposed before. This slow-moving outbreak could soon represent a
much more significant public health problem if left unchecked.

Unfortunately, very few people in the area can access the tools
necessary to diagnose and treat the condition. Ultrasound imaging is
the most effective way to screen for and monitor infections, allowing
healthcare providers to offer people the necessary treatment. By the
time human infections are advanced, expensive operative procedures to
remove hydatid cysts are the only treatment available. Routine
ultrasound imaging over time also helps monitor treatment and surgical
outcome. However, many health facilities lack ultrasound services.

The intersection of infected livestock from endemic tapeworm regions
and dogs scavenging for disposed animal by-products creates conditions
under which it is more likely that humans become infected. As Africa’s
agricultural systems face increasing demands from population growth
and demographic changes, rapid unplanned growth can have devastating
unintended consequences.

To protect populations, systems of surveillance must keep up with the
changing world. Tracking the spread of disease, as we have done with
Echinococcus granulosus in a non-endemic region, is an essential
step to prevent future outbreaks of public health concern.

[Byline: Eric Fevre]

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