Scientists in Kenya have made a breakthrough in the war on tsetse fly by identifying which animals the fly feeds on, in research designed to support strategies to break the fly’s life cycle and stop the spread of the killer disease trypanosomiasis.
The disease costs Africa around $4.5bn a year with around three million cattle dying from tsetse-transmitted trypanosomes every year. In addition, an estimated 70,000 people in 36 countries of sub-Saharan Africa are currently infected with the disease. The most recent epidemic, in Uganda in 2008, caused 48,000 deaths.
However, tsetse flies are notoriously difficult to observe in nature, since they don’t form swarms, preferring to rest alone in bushes waiting for a source of warm blood to wander by. In this, their choices are mainly guided by their sense of smell. This has created big challenges for scientists and public health officials, who need to observe the insects’ hosts to identify what animals they feed on.
A group of farmers assisted by scientists are now courting certain parasites and insects on their farms to act as natural enemies to other plant threatening parasites, in a model described as ‘sending a thief to catch a thief’.
Insects that include Ladybird beetles, spiders, bats and red fire ants, all long vilified as farmers’ greatest enemies, are now becoming farmers’ friends as multiple applications of synthetic pesticides by farmers fail to resolve the problems responsible for four fifths of the country’s harvests losses. Kenya currently spends close to Sh5bn a year on pesticides, much of it to battle insects.
However, the new farmers’ friend insects either secrete unique fluids that chase away pests, or feed directly and swiftly on the pests. According to many farmers, it takes just a week to rid a farm of pests with natural enemies, as against months when using synthetic pesticides.
Ladybird beetles have been in the frontline of the new techniques. The beetles, both in the adult and larvae stage of growth, prey on aphids, leafhoppers, mealybugs, mites, scales and whiteflies, which are known to devour cereals. A single ladybird consumes approximately 200 - 300 aphids over its lifetime of 1-3 months. Farmers have even begun growing wild sunflowers, with a higher pollen count than domesticated varieties, to attract the Ladybirds.
Rove beetles, another of the new friends, eat all stages of a wide range of insects in the soil or in the foliage, including bean flies, cutworms, scale insects and spider mites. Young larvae search the soil for cocoons of flies and after eating the pupa emerge sometime later as adults.
Last year, a unique parasitic wasp was even introduced into the country by the International Centre for Plant and Physiology and Ecology (ICIPE), Agricultural Ministry and Kenya Agricultural Research Institute (KARI) and has recorded impressive results in parts of Rift Valley where it was dispatched to tackle the notorious African fruit fly that feeds on mangoes and avocados.
Orchards that have introduced the wasp, such as Lakita Orchard in Naivasha, have delivered yields of around 10 tonnes a hectare compared with 4 tonnes a hectare when they were using synthetic pesticides.
Beating the fruit fly has been vital to export revenues. The proliferation of the fly on avocados led to an export ban to South Africa that was only recently lifted, and which cost Kenya Sh200m a year for 4 years, particularly hurting smallholders, which account for 85 per cent of Kenyan avocado exports.
Farmers in Busia county of Western Province have even moved from the bugs and parasites to courting bats as predators to fight moths and other insects. “Besides eating tons of insects they have also been feeding on cucumber beetles and even Stink bugs which damage our tomatoes,” said Wekesa, a large scale farmer in Busia who claims bats are the most effective natural enemy of all because they form large colonies and have a huge appetite. One bat can feed on 2kgs of insects nightly, and they forage over large distances.
Scientists have also developed other natural enemies in the laboratories like the Diamond Black moth, which is very swift in feeding on the large grain borer that is catastrophic to both maize and woods. Scientists have been releasing them onto farms when there is an acute invasion of parasites in farms.
The moth provides swift pest control but does not harm the crops and allows for naturally grown food. “I strongly feel when we afford to control all pests without touching any chemicals will be when we say we have passed on a healthy chemical free future to our generation, and one way is embracing an agricultural system that imitates a natural system,” said Dr Ladslas Ritwo, a scientist from the University of Nairobi College of Agriculture and a consistent crusader of organic pest control methods.
Written by Bob Koigi for African Laughter
Goat keepers are recording new cases of a goat disease traditionally confined to pastoralist areas, which is now spreading into other areas including Central and Eastern province, causing a slump in goat prices, by as much as 75 per cent, and prompting the building of a new vaccination facility.
The disease, scientifically known as Peste des petits ruminants (PPR), or plague of small ruminants, threatened to wipe out large swathes of livestock in North Eastern in 2006-2008, when 5 million animals predominantly goats and sheep were infected with 50 per cent of them dying.
The disease also threatened food security in these areas where the population is predominantly pastoralist and relies on livestock for food and income. Aggressive and concerted efforts between government and organisations such as The Food and Agriculture Organization of the United Nations (FAO) greatly reduced cases of new infection. But the gains are now being reversed due to pastoralist migrations with the spread being attributed to close contact between infected and the non infected small ruminants.
Areas in Laikipia and even Kieni in central Kenya have now recorded new cases of the disease, whose immediate symptoms include lassitude, fever, discharges from the eyes and nose, sores in the mouth, laboured breathing and diarrhoea. Farmers rearing the goats have already recorded sever business impacts, with the majority of their goats either dying or the farmers being forced to dispose of the goats at cheaper prices since buyers are wary of the disease.
Muthoki Kihekia, who has reared livestock for a decade in Laikipia, says he has always managed to sell his goats for Sh3000 to Sh4000 when they are in good health, but the goats are now selling for as little as Sh1000, a fact he attributes to buyers flight to safety. “No one wants to buy goats, because they hear that the outbreak of the PPR disease has never been fully been addressed. When we sell them due to lack of pasture, it’s like we are disposing of them, because they attract a very low price,” said Muthoki.
Victor Lomde, another seasoned herder from Turkana District has never recovered from the 2006 plague that claimed 300 of his goats in three months. He, however, made a resolve to have all the remaining livestock vaccinated.
“My veterinary surgeon has taught me a lot. This vaccine works wonders, it’s like the vaccine they give children to prevent them from Polio. Once you have it, you are covered. There have been pockets of outbreaks since 2007, but I can comfortably say that I haven’t recorded any deaths any more.”
The disease, which typically claims the life of the infected ruminant within a month, can easily be contained through frequent disease prevention and control interventions. The PPR vaccine provides protection for about three years for small ruminants.
The spread of the disease, which until recently was considered to be a parochial disease of West Africa, has received international attention, with the FAO recently announcing that its member countries, Kenya included, had passed a resolution shifting the attention of the organisation from rinderpest, an equally notorious and fatal disease among cattle, to the goat disease, after declaring rinderpest eradicated globally.
This followed an announcement in May that the World Organisation for Animal Health (OIE) at its General Session had passed a resolution to the effect that all countries in the world had been formally accredited as free from rinderpest, which had previously been a huge menace to cattle.
As part of the call by FAO to member states to address the plague in their respective countries, the Kenyan government is working on building a KARI vaccine production centre, which will increase the capacity of producing the PPR vaccine with the hope of improving the flock immunity from currently less than 30 per cent to 70 per cent, and reduce annual losses related to the plague by at least 60 per cent by 2013.
Written by Bob Koigi for African Laughter
Kenyan and American scientists have opened renewed research to find an anti-tick vaccine to control East Coast Fever, which still kills thousands of the country’s cattle, by stopping cattle from becoming carriers that pass the disease to uninfected ticks.
The research at the International Livestock Research Institute in Kenya (ILRI) is taking a two-pronged approach to eliminating the disease, which is not a contagious disease, but spread through a parasite that ticks pick up when they bite infected animals.
Farmers in many parts of Africa use a vaccination method against East Coast fever known as infect and treat, where they infect animals with live parasites and then treat them with drugs to help them recover.
This immunizes cattle against a full case of the deadly fever, but means that uninfected ticks that bite the vaccinated animal can still get infected, and spread the parasite on to other animals. The new research is now targeting better ways of killing the parasite itself, through vaccination.
“The development of combined vaccines conferring protection against pathogens transmitted and the respective vector may be a prerequisite for the success of vaccine development against protozoan pathogens, including Theileria parva, the causative agent of East Coast fever (ECF), an acute tick-borne disease causing high rates of morbidity and mortality in cattle in 12 countries in sub Saharan Africa,” said ILRI, unveiling the new research.
“As the livelihood of small-holder farms, often managed by women, is dependent on one or two cattle, the financial burden due to loss of income and livestock products impacts on the quality of all aspects of family life,” it added.
For these reasons, “ILRI is undertaking a research to analyse the transmission of piroplasms from T. parva infected cattle to uninfected nymphal ticks. T. parva is mainly transmitted by the brown-ear tick Rhipicephalus appendiculatus.”
“Additionally, we will attempt to isolate and characterise novel tick gut antigens of R. appendiculatus with the final goals of enhancing the performance of existing tick vaccines that are based on the BM86 antigen.”
According to scientists, current vaccines also require cold storage, adding to their cost and making it difficult to use them in many areas of Africa.
For more than four years, American and Kenyan scientists have studied diseases carried by ticks. The work in the US centered on the parasite that causes Texas cattle fever, which is common to the Americas. But this year, the scientists began a new study in Africa aimed at developing a new vaccine for the East Coast fever parasite that does not require infecting and treating animals or the need for cold storage.
Written by Bob Koigi for African Laughter
However, research scientists at the International Centre of Insect Physiology and Ecology (ICIPE) in Nairobi have now identified the feeding patterns of the flies through a process known as DNA barcoding
Catherine Muturi, a Master’s student at Egerton University, used special traps developed at ICIPE, to catch tsetse flies in Tanzania, Kenya and Uganda, focusing on areas where humans and livestock are regularly exposed to the insects.
The trap is a kind of scarecrow that looks enough like a cow to trick the tsetse fly. Lured by the smell of cow’s urine contained in a bottle, they flies are attracted by the blue cloth on either side of the trap. The black cloth in the middle invites the flies to settle. They then fall into the trap and die.
The flies were then dissected and blood meals were DNA barcoded to determine the sources. Initial barcode analysis of the blood meal showed that most tsetse flies fed from single sources.
Out of 13 engorged tsetse flies caught in the Nguruman area of Kenya, six had fed on African savanna elephants and five on warthogs, while one fly each had fed on an African buffalo and a baboon.
All 12 flies sampled in Busia had fed on cattle.
In the Serengeti ecosystem, wildlife like African buffalo, giraffe, warthog, African savanna elephant and spotted hyena were the “blood donors” to the tsetse flies.
“In Busia, where livestock are the more likely sources of blood, spraying cattle with a suitable insecticide can be an effective strategy,” said Dr. Daniel Masiga, research scientist and Head of the Molecular Biology and Bioinformatics Unit at ICIPE. “However, in areas where wildlife species are the main source of blood for tsetse flies, trapping devices or insecticide treated targets are appropriate.”
In the latter case, tsetse flies pick up a lethal dose of insecticide when they land on cloth treated with the chemical. Scientists at ICIPE have previously shown that certain chemicals, for example those found in bovine urine, attract tsetse flies.
“Knowing precisely what tsetse flies feed on helps us guide control efforts,” says Masiga.
By Bob Koigi for African Laughter
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