Archive for the ‘Disease’ Category

Overprotection of babies may increase the risk for allergies

June 7, 2014

It is often said that one in 3 in developed countries suffer from some of allergy. By the time they are 3 years old half the children in the US suffer from wheezing or asthma. It is often claimed that this is because of the various chemical compounds that modern humans have put into the atmosphere. But I am not so sure that this is the sole cause or even a significant cause. It could be that we are seeing the downside of having an obsession about dirt and being obsessively “antiseptic”  with our children.

Our immune systems need to be triggered and challenged if they are to develop. That is well enough known and is the basic fact exploited by the advances in vaccination science. But the corollary is that when we are overprotective with babies – and especially in the first year of life – a lack of exposure to these triggers prevents the immune system from developing some basic resistances and this may lead to the greater incidence of allergies later on.

It could well be that it is the obsessive cleanliness around our infants which is itself the cause of an underdeveloped immune system and the greater prevalence of allergies.

A new paper finds that some exposure to “dirt” early in life is probably a very good thing.

Susan V. Lynch et al,  Effects of early-life exposure to allergens and bacteria on recurrent wheeze and atopy in urban childrenJournal of Allergy and Clinical Immunology, 2014; DOI:10.1016/j.jaci.2014.04.018

Abstract: 

Wheezing illnesses cause major morbidity in infants and are frequent precursors to asthma. We sought to examine environmental factors associated with recurrent wheezing in inner-city environments. …….. 

Cumulative allergen exposure over the first 3 years was associated with allergic sensitization, and sensitization at age 3 years was related to recurrent wheeze. In contrast, first-year exposure to cockroach, mouse, and cat allergens was negatively associated with recurrent wheeze (odds ratio, 0.60, 0.65, and 0.75, respectively; P ≤ .01). Differences in house dust bacterial content in the first year, especially reduced exposure to specific Firmicutes and Bacteriodetes, was associated with atopy and atopic wheeze. Exposure to high levels of both allergens and this subset of bacteria in the first year of life was most common among children without atopy or wheeze.

In inner-city environments children with the highest exposure to specific allergens and bacteria during their first year were least likely to have recurrent wheeze and allergic sensitization. These findings suggest that concomitant exposure to high levels of certain allergens and bacteria in early life might be beneficial and suggest new preventive strategies for wheezing and allergic diseases.

From the John Hopkins Press Release :

Infants who grew up in homes with mouse and cat dander and cockroach droppings in the first year of life had lower rates of wheezing at age 3, compared with children not exposed to these allergens soon after birth. The protective effect, moreover, was additive, the researchers found, with infants exposed to all three allergens having lower risk than those exposed to one, two or none of the allergens. Specifically, wheezing was three times as common among children who grew up without exposure to such allergens (51 percent), compared with children who spent their first year of life in houses where all three allergens were present (17 percent).

In addition, infants in homes with a greater variety of bacteria were less likely to develop environmental allergies and wheezing at age 3.
 
When researchers studied the effects of cumulative exposure to both bacteria and mouse, cockroach and cat allergens, they noticed another striking difference. Children free of wheezing and allergies at age 3 had grown up with the highest levels of household allergens and were the most likely to live in houses with the richest array of bacterial species. Some 41 percent of allergy-free and wheeze-free children had grown up in such allergen and bacteria-rich homes. By contrast, only 8 percent of children who suffered from both allergy and wheezing had been exposed to these substances in their first year of life.

Not all dirt is bad.

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The Black Death altered European genes

February 25, 2014

A fascinating study and further support for my view that evolution is not about survival of the fittest but is about the deselection of the weakest.

Reblogged from Science magazine:

The Black Death didn’t just wipe out millions of Europeans during the 14th century. It left a mark on the human genome, favoring those who carried certain immune system genes, according to a new study. Those changes may help explain why Europeans respond differently from other people to some diseases and have different susceptibilities to autoimmune disorders.

Geneticists know that human populations evolve in the face of disease. Certain versions of our genes help us fight infections better than others, and people who carry those genes tend to have more children than those who don’t. So the beneficial genetic versions persist, while other versions tend to disappear as those carrying them die. This weeding-out of all but the best genes is called positive selection. But researchers have trouble pinpointing positively selected genes in humans, as many genes vary from one individual to the next.

Enter Mihai Netea, an immunologist at Radboud University Nijmegen Medical Centre in the Netherlands. He realized that in his home country, Romania, the existence of two very distinct ethnic groups provided an opportunity to see the hand of natural selection in the human genome. A thousand years ago, the Rroma people—commonly known as gypsies—migrated into Europe from north India. But they intermarried little with European Romanians and thus have very distinct genetic backgrounds. Yet, by living in the same place, both of these groups experienced the same conditions, including the Black Plague, which did not reach northern India. So the researchers sought genes favored by natural selection by seeking similarities in the Rroma and European Romanians that are not found in North Indians.

Celebrating differences. The migration of gypsies from India 1000 years ago (see map) set the stage for a telling study about how diseases can influence the genome.

Celebrating differences. The migration of gypsies from India 1000 years ago (see map) set the stage for a telling study about how diseases can influence the genome.

Netea; evolutionary biologist Jaume Bertranpetit of Pompeu Fabra University in Barcelona, Spain; and their colleagues looked for differences at more than 196,000 places in the genomes of 100 Romanians of European descent and 100 Rroma. For comparison, the researchers also cataloged these differences in 500 individuals who lived in northwestern India, where the Rroma came from. Then they analyzed which genes had changed the most to see which were most favored by selection.

Genetically, the Rroma are still quite similar to the northwestern Indians, even though they have lived side by side with the Romanians for a millennium, the team found. But there were 20 genes in the Rroma and the Romanians that had changes that were not seen in the Indians’ versions of those genes, Netea and his colleagues report online today in the Proceedings of the National Academy of Sciences. These genes “were positively selected for in the Romanians and in the gypsies but not in the Indians,” Netea explains. “It’s a very strong signal.”

Those genes included one for skin pigmentation, one involved in inflammation, and one associated with susceptibility to autoimmune diseases such as rheumatoid arthritis. But the ones Netea and Bertranpetit were most excited about were a cluster of three immune system genes found on chromosome 4. These genes code for toll-like receptors, proteins which latch on to harmful bacteria in the body and launch a defensive response. “We knew they must be important for host defense,” Netea says.

What events in history might have favored these versions of the genes in gypsies and Romanians, but not in Indians? Netea and his colleagues tested the ability of the toll-like receptors to react to Yersinia pestis, the bacterium that caused the Black Death. They found that the strength of the immune response varied depending on the exact sequence of the toll-like receptor genes.

Netea and Bertranpetit propose that the Rroma and European Romanians came to have the same versions of these immune system genes because of the evolutionary pressure exerted byY. pestis. Other Europeans, whose ancestors also faced and survived the Black Death, carried similar changes in the toll-like receptor genes. But people from China and Africa—two other places the Black Death did not reach—did not have these changes. (There have been multiple plagues throughout history around the world, but none have been so deadly as the Black Death, which killed an estimated one in every four Europeans, and so exerted very strong selection.) The similarities in the other genes were likely caused by other conditions experienced by Rroma and Europeans, but not Indians.

“The use of two populations living in the same geographic area is very clever,” says human population geneticist Oscar Lao of Erasmus MC in Rotterdam, the Netherlands, who was not involved in the study. “This experimental evidence is very important,” he adds. It shows that the Black Death bacterium does indeed interact with the proteins coded for by the genes favored by natural selection. “That should be the goal for all those type of analyses.”

“It’s a nice hypothesis that they are putting forward,” agrees Lluis Quintana-Murci, a human population geneticist at the Pasteur Institute in Paris who was not involved in the study. The genetic changes may have modern-day effects. “The presence of these particular versions of these genes may give the evolutionary basis for why certain populations are more at risk” for certain types of diseases, says Douglas Golenbock, an immunologist at the University of Massachusetts Medical School in Worcester. “The side effect seems to be that the Europeans have a more proinflammatory immune system than those who have never experienced Black Death.”

However, Lao and Quintana-Murci wonder if the convergence in these genes might be explained another way. It’s possible that these favorable versions were introduced into the Rroma by interbreeding between the Rroma and the Romanians, they suggest. Additional sequencing of the converged genetic regions should answer this question, Quintana-Murci says. It’s also important to check how these toll-like receptors respond to other deadly bacteria to see if other diseases might have been the cause of the changes. That will likely happen, Quintana-Murci adds. “This will inspire other labs to see if other bacterial infections could also explain the [selection].”

Callous UN claims immunity to escape compensation for introducing cholera to Haiti

February 22, 2013

The UN has claimed immunity to avoid any compensation for introducing cholera to Haiti.

Sometime in October / November 2010, cholera was introduced into Haiti by Nepali UN troops. These troops were not sufficiently screened by the UN before being deployed and many were carriers of a Nepali strain of cholera. Even though they were being introduced into a region recovering from an earthquake the troops received no information or training regarding good practices regarding sewage handling or preventing the spread of infection.  The outbreak of cholera that was caused by broken sewage pipes from their camp developed into a virulent and catastrophic epidemic  in the infrastructural chaos that prevailed in Haiti after the January 2010 earthquake.  There is little doubt that this was the cause of the outbreak though this has never been acknowledged by the UN. The subsequent efforts made by the UN and the WHO  to fight the epidemic were not also free of criticism. Cheap but untested vaccines were deployed to contain costs. Till UN cholera arrived, Haiti had been free of cholera for over 100 years. Some 600,000 were infected in currently the largest outbreak in the world and almost 8,000 people have died. This virulent South Asian strain of cholera is now established in the Americas.

UN Cholera: image Reuters - Allison Shelley

UN Cholera: image Reuters – Allison Shelley

And now the UN has claimed immunity to avoid having to pay any compensation. The immunity is claimed under its own “UN’s Convention on the Privileges and Immunities of the UN”. Of course the moral compass of the UN is only as good as that of its worst member but considering the overwhelming poverty in Haiti, invoking this convention seems a particularly callous and cowardly path to follow. It would seem that the UN (read the “world community”) does not put a very high value on a Haitian life. Cheap troops, cheap vaccines, cheap practices and no compensation! Perhaps the “world community” represented by the UN believes that Haiti has already received more than its fair share of economic support?

BBC: 

The United Nations has formally rejected compensation claims by victims of a cholera outbreak in Haiti that has killed almost 8,000 people. UN Secretary General Ban Ki-moon called Haitian President Michel Martelly to inform him of the decision.

The UN says it is immune from such claims under the UN’s Convention on the Privileges and Immunities of the UN. Evidence suggests cholera was introduced to Haiti through a UN base’s leaking sewage pipes. The UN has never acknowledged responsibility for the outbreak – which has infected more than 600,000 people – saying it is impossible to pinpoint the exact source of the disease, despite the mounting evidence the epidemic was caused by poor sanitation at a camp housing infected Nepalese peacekeepers. 

In a terse statement, Mr Ban’s spokesman said damages claims for millions of dollars filed by lawyers for cholera victims was “not receivable” under the 1947 convention that grants the UN immunity for its actions. …… 

……. The lawyer, Brian Concannon, said the victims’ legal team would challenge the UN’s right to immunity from Haitian courts, on the grounds that it had not established an alternative mechanism for dealing with accountability issues, as stipulated in its agreement with the government.

He also said lifting immunity would not challenge UN policy, which is protected by the convention, but its practice, such as how to test troops for disease and properly dispose of sewage.

Mosquitos increasing in the UK but global warming not blamed – yet

August 23, 2011

This is a very mildly interesting story from the BBC.

I read every word and realised that I continued reading long after it had ceased to be interesting only because I was waiting for the punch line that it “was all due to global warming”.

It never came.

But it will.

Based on a survey of UK local authorities, reports of mosquito bites over the last 10 years are 2.5 times greater than in the 10 years up to 1996. NHS Direct statistics show 9,061 calls in England complaining of bites and stings from early May this year to now – up nearly 15% from last summer. Not all bite complaints are due to mosquitoes – many can be attributed to bedbugs, midges and fleas.

But conditions in the UK, particularly in southeastern England, are increasingly hospitable to mosquitoes.

“The wet weather through May and June this year, along with a warm summer, has affected the population because mosquitoes like the standing breeding water,” says zoologist Michael Bonsall at Oxford University. …. 

But once upon a time, malaria-carrying mosquitoes could be found in the salt marshes of southeastern England. It is believed that malaria – literally “bad air” – dates back at least to Roman times in the UK, and outbreaks occurred as recently as the years just following World War I.

British doctor Ronald Ross, who discovered the malarial parasite living in the gastrointestinal tract of the Anopheles mosquito in the 19th Century, recruited teams to eliminate the larvae from stagnant pools and marshes. … 

Malaria in England had effectively died out by the 1950s, mostly due to the draining of much of the marshland where mosquitoes bred. But because of the growth of global travel, the number of imported cases of the disease in the UK has risen, with nearly 2,000 a year today.

Go to BBC article 

 


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