News brief
Declining
deaths to BSE Declining deaths to BSE
Cases
of Bovine Spongiform Encepalopathy (BSE), otherwise known as mad cow disease,
are declining worldwide. According to FAO, the number of BSE death has
decreased at a rate of 50 per cent a year over the past three years. In
2005, less than 500 animals died of BSE around the world compared with
over three times this number two years previously. Tens of thousands of
animals were reported to have died during 1992 at the height of concerns
over BSE. The incidence of variant Creutzfeldt-Jakob Disease (vCJD) is
also waning with only five deaths reported, all in the UK, in 2005 compared
to 18 in 2003. Whilst these declines are encouraging, FAO warns that vigilance
is still required and that measures introduced to detect and control the
disease must continue to be applied. FAO, with assistance from Swiss experts
has been conducting training courses, particularly for developing countries,
on BSE diagnosis, surveillance and prevention in the animal feed and meat
industries.
In China, scientists are reported to have cloned a cow "with gene cells
resistant to mad cow disease". The calf was cloned at Shandong's Laiyang
Agro-Science Institute from cells of an adult cow and carries transplanted
genetic material conferring BSE resistance. In a note of caution, however,
the scientists say more tests will be needed to confirm that the procedure
was a success.
Concerns over carbon and nitrogen emissions
One of the largest increases in CO2 levels ever recorded was reported for 2005, pushing it to an unprecedented level. CO2 levels are now at 381 parts per million (ppm) - 36 per cent (100 ppm) above the pre-industrial average and the highest level for over 650,000 years. The rate of increase of atmospheric carbon dioxide is accelerating, says the US National Oceanic and Atmospheric Administration (NOAA) and appears to confirm the trend that, on average, double the rate of increase has been recorded for recent years compared to 30 years ago. A report from the World Meteorological Organisation (WMO) for 2004, however, stated that increases appeared to be slowing slightly.
Concerns over nitrogen emissions, such as burning of fossil fuels and
livestock keeping, from developing nations have been raised by researchers
who state that plant life in many biodiversity hotspots could be seriously
under threat during the next fifty years. Scientists at the UK Universities
of Sheffield and York found that in the mid-1990s, the average amount
of nitrogen deposited on the planet's 34 biodiversity hotspots, home to
half of all global species, was more than 50 per cent higher than the
global average. Rapid population growth and industrialisation in developing
countries is the major contributing factor to rising emissions and researchers
state that nitrogen deposition could more than double by 2050 should nitrogen
emissions continue as anticipated.
Banana wilt spreads to Tanzania
Bacterial
wilt has been discovered in villages in the Kagera region in north-west
Tanzania. The disease, which has spread rapidly in Uganda since it first
occurred in 2001 and now affects almost all banana growing districts,
has also been identified in Democratic Republic of Congo and Rwanda during
the past two years (see also Uganda's
war on wilt). In Uganda, Banana Bacterial Wilt (BBW) which is caused
by the bacterium Xanthomonas capestris pv. Musacearum affects all
banana types and causes wilting and premature ripening of the fruit. The
disease remains a significant concern in Uganda, but quick adoption of
control measures by farmers is yielding positive results as incidences
decline and production picks up.
In Tanzania, the affected districts of Muleba and Karagwe are important
banana producing areas with more than 90 per cent of bananas transported
to markets outside Kagera. Efforts to advise and train farmers in affected
areas are currently constrained by a lack of resources and there are concerns
that the disease will spread more widely. Experience shows that once the
wilt has become established in a plantation, control is very difficult
and eradication is effectively impossible. Disease control relies on removal
of the male bud to prevent insect transmission of the disease, cleaning
of tools and burying of all diseased material.
Genetically modified mosquitoes
For the first time, scientists have bred mosquitoes which are resistant to Dengue fever and capable of passing the resistance to their offspring. Researchers exploited a weakness of the dengue virus 'Type 2', the most prevalent strain. This vulnerability occurs when the virus replicates. After the virus has replicated and been transmitted, it self-destructs. However, scientists have found a way to speed up this process, so that the virus has no opportunity to replicate, in effect making the strain benign.
Dengue fever is spread through the bite of the Aedes aegypti mosquito.
Each year, the virus infects 50 million people in the developing world,
killing about 20,000. If this method of resistance to the virus can be
reproduced in wild mosquitoes, fewer insects would transmit the virus,
reducing its spread. Researchers now want to improve the method so that
it works for all four strains of the virus rather than only one. They
will also explore ways of inserting the gene so that it can be spread
through wild populations.
