Science - April 14, 2010

Separating the sheep from the goats

Text:
Broer Scholtens

The Health Council of the Netherlands is currently looking into the need for vaccination against Q-Fever, but it is unlikely that people living within goat farming regions will soon be given an injection. The disease needs to be tackled mainly at the source: vaccinating goats and sheep, and clearing infected farms. Despite these measures, this year is not going to see the end of it yet.

Goats in a farm in Sellingen, Groningen, are vaccinated against Q-Fever
The Netherlands is gripped by the Q-Fever. This bacterial infectious disease has reached epidemic proportions in the last few years. Despite widespread vaccination of goats and clearing of infected farms, the epidemic is continuing its spread, with the number of cases this year already exceeding that in the same period last year. A part of this increase is caused by heightened publicity for the disease, which makes people more alert and quicker to take their ailments to the doctors. 
By far, most of the infections are found in the 'Heart of Brabant' in the north-eastern part of the province of Brabant, south of Den Bosch, where large goat farms are located. This is also the area with the largest number of affected goat farms, and therefore most animals culled, thereby pointing to a direct relation between infected goats and disease occurences in humans.
Besides the clearing of affected farms, much hope has been pinned on the vaccination of all sheep and goats. Vaccination started on a small scale in 2008, mainly in Brabant. In 2009, it was also carried out in other areas. This year would see a move across-the-board; for the first time, goats and sheep will be vaccinated nationwide. And this has to be completed before June.

Manure
Vaccination would put a total stop to the outward spread of the Q-Fever bacteria from the barns; this effect is expected to be felt from 2011, at the earliest. It is suspected that bacteria are spread across the country via manure. Bacteria enter the manure mainly during births, especially in premature miscarriages - which is common in goats. When a pregnancy is aborted, billions of Coxiella burnetii bacteria, which cause Q-Fever, find their way via the amniotic fluid into the manure. When lambs are born in spring, bacteria discharge takes place too, but on a much smaller scale, being several millions per birth.
Dairy goats are kept in barns, where fresh manure (with a lot of bacteria) is covered daily with a new layer of straw. The barn is cleaned every few months; the dried manure is then spread out over the soil. The bacteria present in the manure can be carried by the wind across a distance of many kilometres, with a big chance that people would inhale the bacteria and catch the disease. Moreover, most goat barns are open-air, allowing manure particles containing bacteria to be spread directly to the surroundings. Vaccinating goats will almost entirely eradicate the chances of a miscarriage, as recent research shows, thereby lowering the chances of the bacteria spreading across the country. It is believed that over time, less people will fall sick. Disease spread via manure is a specific Dutch problem as many large goat farms are located in densely populated areas.

Blisters
A Q-Fever vaccine for humans has been available for many years. The Q-Vax - based on dead bacteria cell material - is licensed only in Australia, the country where Q-Fever was discovered eighty years ago. Beginning from ten years ago, those in related occupations, such as slaughter house workers and sheep shearers, are given vaccinations, thus reducing the number of infections from six hundred to two hundred a year.
The vaccine is very effective: 83 to 100 percent of those vaccinated are protected for at least five years, according to research results. However, such studies involved only small numbers of people and were carried out within a short period of time. Side effects have been recorded in these studies, particularly near to the injected area, usually the upper arm. Skin irritations can break out, some of which develop into blisters, especially in people who have been infected before and have developed anti-bodies in their blood. Very serious side-effects could be prevented by vaccinating only those who have never been infected or have been vaccinated before. In Australia, only such 'clean' persons are given vaccinations. 
'Buy this human vaccine' is the advice given by the Australian microbiologist-cum-epidemiologist Stephen Graves to Dutch agriculture experts at the end of February. Test it among goat farmers and their families to find out if it also works against the bacteria strain making its rounds in the Netherlands. Heeding this advice, Health Minister Ab Klink has asked the Health Council to issue a recommendation about the necessity for vaccination. This will be given in June.

Heart patients
Many questions still need to be answered. Can the Australian vaccine be used here? It hasn't been formally admitted into Europe and the US, has it? Who will get an injection? The occupational groups, their families and those living in the surroundings?  How far are the surroundings from the barns? Should this apply only to heart patients who will suffer from serious complications if they get Q-Fever? 'I can't say much', declares Fred van Zijderveld of the Central Veterinary Institute (CVI) of Wageningen in Lelystad. He sits on the Health Council committee which is working out the recommendation. 'Possibly the occupational groups, but not the general population', is all he wants to add.
However, vaccinating the occupational groups and their families does clearly have a constraint. Many workers in these groups have in the (distant) past - often without knowing - been infected before. Because of the high risks of serious side-effects, most of them will be exempted.
That leaves only heart patients for the vaccination campaign, or - as advocated by doctors of the Jeroen Bosch Hospital in Den Bosch to the minister - people who are vulnerable, often the elderly. But there is little experience in this area. Those vaccinated in Australia are mostly young and healthy men. 'Very little is known about the side effects in a specific risk group such as heart patients', warned Van Zijderveld. 'The Health Council has asked Australia for more information.'

Osterhaus
Virologist-cum-veterinary microbiologist Ab Osterhaus of the Erasmus Medical Centre in Rotterdam, adviser to the Health Council, doubts the necessity of mass vaccination. 'The risk of side effects is too high. Ten percent of those vaccinated will suffer from these in one way or another. This amount is very much higher compared to, for example, the side effects from the flu vaccine. Q-Fever is a localized problem compared to other infectious diseases. It's not realistic to vaccinate the entire population in an area against Q-Fever because of the high risk of side effects', adds Osterhaus, speaking for himself. 'The Q-Fever problem has to be tackled at the source: clear infected farms and vaccinate all goats. We may need to consider vaccinating risk groups such as heart patients in infected areas.'

Since the beginning of this year, 265 cases of Q-Fever have been reported at the Municipal and Regional Health Service (GGD). Last year, general practitioners registered 2365 Q-Fever patients. There were 168 patients at the start of the epidemic in 2007. Before that, the number of cases was no more than 20 annually. The disease has claimed ten lives since 2007. The figures are indicative, warns the National Institute for Public Health and the Environment (RIVM); probably more people were infected than met the eye, especially in the past years. Symptoms such as fever, coughing and headaches do not point straight to Q-Fever. Only laboratory examination can give a definite diagnosis about this bacterial infection. In the meantime, doctors are on the alert for the disease, and  more lab examinations are being carried out. 

 

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