Eradicating a Tick in Time...

Tiny, tenacious and a pernicious, disease-carrying pest of livestock, the tropical Bont tick has been island hopping in the Caribbean for more than 170 years. In a consolidated effort to break the tick's hold and prevent its possible spread to mainland Central America, a joint programme between the international community and the Caribbean islands has led to the near-eradication of the pest on four islands (Dominica, Montserrat, St. Kitts and St Lucia). However, the elimination of remaining 'hot-spots', although small, is remaining elusive and further investment and technical support will be required if this costly pest is to be eradicated.

The large and brightly-coloured tropical Bont tick, Amblyomma variegatum, hitched its way to the Caribbean from Africa almost two hundred years ago when infested cattle from Senegal were imported into Guadeloupe. Since then it has spread steadily island to island, probably with movements of cattle and, perhaps, in larval and nymph stages, in the blood of a migratory bird, the cattle egret. And, although the mature tick's preferred host is domestic cattle, it also infests sheep, goats, horses and dogs and can survive on wild animals as well. In some area, it may also bite humans causing intense skin irritation and inflammation.

Counting the cost

For animal, the tick's bites are nasty and often develop into a septic wound or abcess, which can damage teats, hides and skins. However, far worse than its bites are the diseases associated with this tick. As it feeds, the highly infectious disease Cowdria ruminantium -which causes heart water (cowdriosis) - can be passed to the host reducing meat and milk production and, in severe cases, resulting in death. Acute dermatophilosis in cattle, a skin disease caused by bacteria Dermatophilus congolensis has also been linked with infestations. The tropical Bont tick and its associated diseases already cause huge losses in productivity. On the island of Nevis, for example, 90% of cattle and 70% of small ruminants died from dermatophilosis when the tropical Bont tick invaded.

The livestock industry in North, South and Central America is right to keep a watchful eye on the progress against the tropical Bont tick in the Caribbean. If the tick reaches their shores, the havoc it could cause can only be guessed at. The principal fear is heartwater. Two widely distributed indigenous ticks, A. maculatum, the Gulf Coast tick, and A. cajennense, the Cayenne tick have been shown, experimentally, to transmit the disease. If the Caribbean Bont tick were to find its way to the mainland, heartwater could rapidly become established making elimination difficult if not impossible. Researchers estimate that a tropical Bont tick infestation on the American continents could cost the livestock industry almost US$800 million.

Control in farmers' hands

However, it is possible to eradicate the tropical Bont tick. It was eliminated from several of the northernmost Caribbean islands in the 1980's and 1990's but re-infestation occurred and quickly had to be dealt with. And now, through the co-ordinated efforts of the Caribbean Amblyomma Programme (CAP), a participatory approach with local livestock producers and government staff is proving effective. The co-operation and commitment of animal owners has been crucial as farmers were asked to apply the approved acaracide to their stock every two weeks for at least two years. In medium and low risk areas the emphasis has been on information and awareness campaigns and effective quarantine systems for animals bought in from other islands.

The cost of CAP has been about US$20 million over a six-year period. Further funding has recently been from the European Community to continue current eradication and surveillance efforts. The cost may seem high but, measured against the potential cost if the tropical Bont tick reached the American continents, those involved say it is a small one to pay for the elimination of a costly pest from the entire Western hemisphere.

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