From Calcutta to New Jersey .... the mosquito diaries :-)

If people can move, so can other animals.  And, thus, even can mosquitoes!

A couple of years ago, I ran into trouble (ed: when have you not run into trouble?!) for writing an opinion column that as long as humans move around the world, there will always be invasive species.  And, because there is no way we would ever force people to stay put, well, we can only expect more and more of species appearing in habitats far, far away from their original homes.

The latest in the example here is mosquitoes. (HT)

The modern city of Kolkata sits toward the western end of what could, until recently, have been called the natural range of the Asian tiger mosquito: a swath of land stretching from Pakistan to North Korea. Its ancestral habitat is in the forests of Southeast Asia, where it laid eggs in water-filled tree holes or the hollow insides of bamboo stalks, rarely travelling more than a few hundred metres from the cavity where it was born.

Over the course of the past two or three decades, however, the Asian tiger mosquito has become considerably, prodigiously more mobile. It has circled the planet, emerging in Trinidad in 1983; Mexico in 1988; France in 1999; Cameroon in 2000; Nicaragua, Greece, Israel and Switzerland in 2003. It has colonised North and South America, Africa, and Europe, until it has become a great nuisance in Brazil, Albania, Nigeria, Mexico and Italy – “the most invasive mosquito in the world”, a team of researchers wrote in 2007, in the journal Vector-Borne Zoonotic Disease. The mosquito from the Southeast Asian jungle is also now a great nuisance in Trenton, New Jersey – the greatest present-day mosquito nuisance in a wetland state whose history is written in waves of mosquito infestation.

What is the problem, you ask?

The Asian tiger mosquito is capable, in laboratory testing, of carrying and transmitting a variety of viruses, but so far, in the wild, it has been a less effective vector of disease than the yellow fever mosquito, with one notable and alarming exception. An outbreak of chikungunya – a virus that causes high fever and lingering joint pain – on the island of La Reunion in 2005, which infected 266,000 people and killed 248, was traced to a mutation in the virus that enabled it to be transmitted by the Asian tiger mosquitoes. Two years later, a tourist who had been in the Indian Ocean region passed through Ravenna, Italy. There, he encountered a local population of Asian tiger mosquitoes, which had arrived from the United States in a shipment of tyres. The convergence led to Europe’s first outbreak of the disease – and raised the possibility not only of chikungunya continuing to follow the mosquitoes around the world, but of diseases such as dengue or yellow fever making the same mutational leap. 

Of course, we then launch a war on mosquitoes:

New Jersey is merely the northern fringe of the Asian tiger mosquito’s US territory, which now includes the entire southeast, from the Gulf of Mexico across the south and more than halfway up the Atlantic coast. Mercer County and neighbouring Monmouth County, which together form a belt across the middle of the state, are in the second year of a five-year, $3.8 million project, backed by the United States Department of Agriculture, to try to bring the invading swarms under control.

Maybe yet another war we are going to lose!