By Mary Hearty
There is risk that the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) among camels and humans in the horn of Africa may mutate with time, and gain power in human to human transmission, thus present a major health concern globally.
Prof Kariuki Njenga, Professor of Infectious Diseases at Washington State University and Senior Research Officer at the Kenya Medical Research Institute (KEMRI) made these remarks when presenting findings of a project dubbed: Tracking the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) among camels and humans in the horn of Africa during one of the plenary sessions of the 11th KEMRI Annual Scientific & Health (KASH) Conference held virtually from June 8 to 10, 2021.
The virology professor said that they studied genetic variations of MERS-CoV to understand why there was less and mild human infections in the horn of Africa unlike other regions like South East Asia.
“We ended up isolating 9 strains from Marsabit in Kenya and noted that it is actively changing and new variants are emerging,” he explained.
It is for this reason that Prof Njenga advised: “We need to continue watching the virus variants and carry out phenotypic studies because we do not know what continuous mutations may present particularly for the public health.”
The senior researcher said that the aim of their study as they travelled northwards to Marsabit to look for this virus was to isolate and characterize MERS-CoV in East Africa among camels and camel handlers, and to describe the epidemiology of camels and human infection using this virus.
Thus, they recruited 243 infant camels in 33 herds and 262 camel handlers. The infant camels were as young as one day old to one year. The camel handlers were recruited to detect if they were also infected.
“Every two weeks we would sample the camels and collect deep nasal, and 10ml of blood for clinical tests at KEMRI lab as well as look for respiratory infection. We also did a monthly questionnaire,” Prof Njenga narrated.
In 2019, during the MERS-CoV outbreak in camels, 15 of the 33 herds were affected, and 34 percent of the 243 camels were affected. On the other hand, there was only 3 tested positive cases of the 262 sample of camel handlers, and they were asymptomatic. Two of them were male and one female, spouse to one of the camel handlers.
Furthermore, the study on maternally derived antibodies and MERS-CoV infection in one herd found out that maternally derived antibody in infant camels fell to below detectable levels by 8 months of age followed by MERS-CoV infection in the vulnerable herds during the outbreak.
In one herd, the outbreak lasted 8 weeks and affected 11 of 16 calves. Nevertheless, the virus lasted between 2-4 weeks in most calves, accompanied with brief viral shedding enough to cause human disease.
According to their findings, the virus can stay in camels for a very long time since they are long lasting animals and this gives them the capacity to continuously transmit this disease to humans who stay with them.
Another finding was that households that have large herds as much as 25 camels are likely to have higher transmission and detecting positive camels, and also in nomadic households who move camels from one place to the other.
Most of the camel handlers sampled were males accounting for almost 70 percent, mostly young. Over 50 percent of them were under 20 years, whereas 80 percent of the handlers were under 40 years.
Prof Njenga noted that this was an advantage because they were fairly robust and could move from place to place. However, if this study was looking for the transmission of this disease from camel to humans, the professor said that this was not the best population because just like COVID-19, it affects the elderly and people with underlying issues more.
Therefore, he clarified that further studies are still ongoing to particularly among people with underlying conditions like diabetes, cancer, cardiovascular disease, among others, whether they can develop symptoms when they get infected.
The study was conducted in the Horn of Africa region – Eritrea, Ethiopia, Somalia, Kenya and Djibouti –specifically, Northern Kenya. Marsabit County in Northern Kenya is home to over 65 percent of all the world’s dromedary camels, that is, about 21 million; this means that the region harbors almost two-thirds of the camels that contain MERS-CoV.
According to the Virology Professor, dromedary camels are two types in the world. The ones found in Asia with two humps, and those with one hump. This disease affect only the one-hump camels.
Studies in this camel population in Kenya and the neighboring countries like Ethiopia have shown that there is a wide spread of antibodies among the camel population and this shows that the virus is robustly transmitted among the camel population.
Prof Kariuki said that some studies have shown up to 95 percent of positive camels in regions like Marsabit, Isiolo and other regions that they have sampled. Other studies have even shown 75% to 78% of positivity. “There have also been a recent 2-year study that have allowed us to detect some viral RNA from camels in Sudan, Ethiopia and Eritrea,” he added.
On the other hand, in humans, he said: “There has really not been much. There was a paper that was published from Kenya by theory that showed antibodies in just two humans but not much, which was very strange because the antibodies that were detected had not even travelled so we were puzzled how they would have got the disease.”
Despite the place being occupied by two-thirds of the dromedary camels, there has been no outbreak of MERS-CoV in Africa, particularly the horn of Africa, as opposed to South East Asia where extensive outbreak that is, over 2500 cases have been reported, and over 800 deaths have occurred.
In fact even in Kenya, the virology expert noted: “We have been looking but we have not found even a cluster of pneumonia that would suggest that we have MERS-CoV. We wanted to look for this virus in camels because that is where we have showed that 85% of the camels have antibodies.”
The first human MERS-CoV cases were first reported in Middle East, where the virus jumped from camels to humans. And the reason why this virus is not feared as COVID-19 is because when it jumps to humans, the transmission does not seem to progress very long as it dies with time in two to three people.
Although, there is still no evidence that the virus can be highly transmissible. The cases of human to human transmission in North America, Southern East Asia, and Europe were particularly in healthcare workers but they died.