My Science School

Vitamin D is a prohormone that is essential for normal absorption of calcium from the gut, and deficiency of vitamin D is usually more common than either isolated calcium or phosphorus deficiency and is the commonest cause of rickets/osteomalacia.

Vitamin D is essential for skeletal health. It promotes differentiation of enterocytes and the intestinal absorption of calcium and phosphorus. This helps in bone mineralization. In conditions of hypocalcemia or hypophosphatemia, vitamin D stimulates bone resorption, thereby maintaining serum levels of calcium and phosphorus. Vitamin D deficiency or resistance thus causes hypocalcemia and hypophosphatemia. Hypocalcemia stimulates the release of parathyroid hormone (PTH), which, through its actions on bone and kidney, partially corrects the hypocalcemia but enhances urinary phosphate excretion, leading to hypophosphatemia and osteomalacia. 25(OH)D also plays an important role in extraskeletal health. Vitamin D deficiency may be associated with certain immunological conditions such as multiple sclerosis, type 1 diabetes, rheumatoid arthritis, inflammatory bowel disease, mood disorders, and cancers such as breast, prostate, and colon cancer. In adolescents, low serum vitamin D levels are associated with increased risk of hypertension, hyperglycemia, metabolic syndrome, and higher risk of upper respiratory infections. This chapter focuses on the skeletal manifestations of vitamin D deficiency.

 

Picture Credit : Google

Denmark's decision to cull millions of minks over coronavirus fear has shocked animal lovers around the world. While the scientific community is divided over the validity of the concern, we will take a look at what is culling and why it is carried out in the first place.

Denmark began culling millions of minks over coronavirus fear last month. A mutated form of coronavirus that can spread to humans was found among minks in hundreds of fur farms in the country. More than a dozen people were found to have caught the infection from the animals. However, there is no evidence that the mutations that originated in minks pose an increased threat to humans.

Denmark is the world's biggest producer of mink fur and its main export markets are China and Hong Kong. Mink farms have been found to be reservoirs of the coronavirus with over 200 of the 1,200 farms affected. Danish scientists are worried that genetic changes in mink-related form of the virus have the potential to render future vaccines less effective. Global health officials are now considering minks a potential risk, particularly in the midst of a resurgence of the virus in the human population. Denmark decided to cull all the minks in the country (instead of just the ones in the affected farms) as a precautionary step to protect people from contracting the virus. But later rolled back the order as it did not have the legal basis to kill all the animals.

While some scientists feel the concerns over mutated strain are exaggerated, others think the virus could jump from minks to other animals. Let's take a look at what culling is and why is it being done...

What is culling?

Culling is the organised and systematic elimination of sick or surplus farm or wild animals and birds, Culling or the selective slaughtering is carried out by authorised wildlife officials with proper permits and approvals.

Why are they culled?

• Mass killing of birds and animals are carried out when they are infected with a contagious disease. It is done to avoid the spread of the disease to other animals and humans. For instance, in the United Kingdom badger culling has been carried out for years to control the spread of bovine tuberculosis (bTB). Badger is a carrier of bTB.

• Aggressive invaders, such as invasive birds that take over nesting sites or attack native birds, are culled to save the local ecological balance.

• Culling is carried out to keep certain animal and bird populations in check. Unusual population growth may cause an imbalance in local ecology, disrupting food sources and other essential resources. In certain parts of Australia, kangaroos are considered vermins (pests), because they damage crops and compete with livestock for scarce resources. Kangaroos are involved in more than 80% of vehicle animal collisions there. In some places of the country, kangaroos are said to outnumber humans.

How is culling perceived by experts?

Culling has always been controversial. On one side, conservationists support it for the common good of all the species in an ecosystem. They perceive culling as a necessary means to protect native biodiversity. But on the other side, animal activists protest over the effectiveness and humaneness of different methods of culling. They oppose when governments resort to culling as a short-term measure Opposition also comes from the perception that every animal should have the right to live.

 

Picture Credit : Google

The first human cases of COVID-19, the disease caused by the novel coronavirus causing COVID-19, subsequently named SARS-CoV-2 were first reported by officials in Wuhan City, China, in December 2019. Retrospective investigations by Chinese authorities have identified human cases with onset of symptoms in early December 2019. While some of the earliest known cases had a link to a wholesale food market in Wuhan, some did not. Many of the initial patients were either stall owners, market employees, or regular visitors to this market. Environmental samples taken from this market in December 2019 tested positive for SARS-CoV-2, further suggesting that the market in Wuhan City was the source of this outbreak or played a role in the initial amplification of the outbreak. The market was closed on 1 January 2020.

On 11 February 2020, the International Committee on Taxonomy of Viruses adopted the official name "severe acute respiratory syndrome coronavirus 2" (SARS-CoV-2). To avoid confusion with the disease SARS, the WHO sometimes refers to SARS-CoV-2 as "the COVID-19 virus" in public health communications and the name HCoV-19 was included in some research articles.

The general public often call both the virus, and the disease it causes, "coronavirus". U.S. President Donald Trump referred to the virus as the "Chinese virus" in tweets, interviews, and White House press briefings, which drew some criticism that he was stigmatizing the disease with racial or nationalistic overtones.

 

Picture Credit : Google

The novel coronavirus disease, COVID-19, has spread to almost every country in the world ever since it was first recorded in China last year, drawing parallels with some of history's most deadly pandemics from 1900 to now. A pandemic is the worldwide spread of a new disease. From 1900, there have been four influenza pandemics. They are:

The Spanish flu shook the world towards the end of WWI. It was the most severe pandemic that claimed the lives of at least 50 million people between 1918 and 1919. The crowded conditions of military camps and the poor nutrition of people during wartime contributed to its spread. Initially observed in Europe, the U.S. and parts of Asia, it had infected nearly 500 million people, mostly youngsters. Despite its name, it did not originate in Spain. As Spain was a neutral side during the war, its media could publish uncensored reports about the illness and the name stuck. Scientists are still unsure of the source of the flu, which was caused by an H1N1 virus of avian origin.

The Asian flu claimed the lives of 1.1 million people worldwide between 1957 and 1958. It was in early 1957 that a new influenza A (H2N2) virus emerged in East Asia, which triggered the pandemic said to be a new combination of avian and human flu viruses, it subsequently spread to Hong Kong, Singapore, Taiwan, India, the U.K. and the U.S. It affected both the young and the elderly. A vaccine developed and deployed soon after slowed down its spread.

The Hong Kong flu emerged in 1968. Caused by a strain of H3N2 virus which descended from H2N2, it was largely seen as a result of the Asian flu of 1957. The third flu pandemic of the 20th Century claimed the lives of 1 million people.

The Swine flu outbreak claimed the lives of over 5 lakh people between 2009-10. It was initially detected only in people with regular exposure to pigs. Caused by a new strain of H1N1 which originated in Mexico, the Swine flu mostly affected children and youngsters. In about a year, 1.4 billion people worldwide were infected by the vines. Swine flu is a highly contagious respiratory condition. A vaccine has been developed for it.

The 1980s and AIDS: HIV (human immunodeficiency virus) leads to AIDS (acute immunodeficiency syndrome) in humans, if left untreated. This virus deeply affects the immune system, especially the cells that help the body fight off infections. HIV was first identified in the Democratic Republic of Congo in 1976. Scientists traced its source to a virus found in the chimps in Africa, which most likely mutated and crossed over to humans. The virus steadily spread to several parts of the world. AIDS was declared a pandemic in the 1980s. It is estimated to have claimed over 30 million people worldwide, with millions more still infected. Till date, no effective cure has been developed.

COVID-19: The coronavirus outbreak emerged in Wuhan City. China, in December 2019. It is a zoonotic disease caused by the novel SARS-CON-2 which most likely came from bats. The World Health Organisation announced COVID-19 as a pandemic in March 2020. As the novel coronavirus causes respiratory problems and can be transmitted from person to person standard precautionary measures such as frequent hand washing maintaining social distancing and mask wearing are being followed Scientists are racing against time to develop vaccines and treatments for COVID-19 which has already claimed over a million lives.

 

Picture Credit : Google

Chytridiomycosis

Chytridiomycosis is an infectious disease that affects amphibians worldwide. It is caused by the chytrid fungus (Batrachochytrium dendrobatidis), leading to deaths in frogs, toads and salamanders. A report released in 2019 revealed that it has caused declines in at least 501 frog and salamander species in the last 50 years.

Of these, some 90 species are presumably extinct in the wild and 124 are suffering serve declines due to the disease, the report said. In many species, the fungus is the main factor in the deaths, but in others, it’s a combination of the disease and other factors such as habitat loss, climate change and predation from invasive species.

Chytrid fungi that infect vertebrate species live in water or soil. They reproduce asexually and have spores that swim in the water. Amphibians contract the disease when their skin comes in contact with water containing spores or with other affected amphibians. The fungus affects their skin, making it difficult for them to breathe (amphibians use their skin for respiration). The fungus also damages the nervous system, affecting their behaviour. It doesn’t kill the amphibians immediately, which increases the odds of the pathogen spreading rapidly.

The disease is thought to have spread around the world via the pet and meat trade.

Chytridiomycosis has affected amphibian populations in more than 60 countries, with the largest die-offs in Australia, Central America and South America.

Devil Facial Tumour Disease

The Tasmanian devil, a marsupial native of Australia, has suffered a dramatic population decline due to Devil Facial Turmour Disease (DFTD). First discovered in northeastern Tasmania in 1996, the disease has since spread across 95% of the species’ range. Up to 90% of their populations have been wiped out.

The disease is spread through biting during fighting or mating. It spreads particularly when canine teeth come into contact with the diseased cells. The rough cells then settle down in their new host, developing into tumours on face, neck and other parts of the body. The devils soon find it difficult to eat and drink, and usually die from starvation and dehydration. The cancer also affects other bodily functions such as respiration and blood circulation. An infected devil dies within six months. According to some predictions, DFTD could wipe out wild Tasmanian devils in less than 40 years.

White-Nose Syndrome

White-Nose Syndrome (WNS) is a fungal disease that has killed over six million bats in North America in over a decade. Caused by the fungus Pseudogymnoascus destructans, or Pd, the disease has spread to 33 U.S. States and seven Canadian provinces. Some populations have declined by more than 90 % within five years of the disease reaching a site. As of 2017, 15 bat species have been affected by WNS.

The fungus infects the skin on the nose, mouth,ears and wings of hibernating bats. The fungus thrives in cold and humid environments such as caves and mines used by bats. Bats can catch the fungus from physical contact with infected bats. The signs observed in bats with WNS include unusual winter behaviour-they experience frequent arousal from sleep and instead of continuing with the hibernation, the bats fly far out of their caves, even in daylight. As a result they quickly drain their fat reserves, and starve to death, Infected bats also show evidence of blood acidification and dehydration.

Sea Star Wasting Syndrome

Sea Star Wasting Syndrome (SSWS) has been linked to the mass die-offs of starfish and several other echinoderms (such as sea urchins, sand dollars and sea cucumbers) since 2013 in the Pacific waters from Mexico to Alaska. In 2014, it was suggested that the disease is caused by densovirus; but subsequent work revealed that an association between a viral pathogen and SSWS was unlikely.

The symptoms begin with white lesions on their limbs, decay of tissue surrounding the lesions and loss of limbs. The sea star would eventually turn into a mushy blob and die. Forty species of sea stars have been affected by this disease.

Research has shown that warming ocean temperatures could play a role in exacerbating the disease. But the actual causative agent for SSWS remains elusive.

Hemorrhagic Septicemia

One day in May 2015, a handful of saiga antelops were found dead in the steppe of Kazakhstan. The next day saw more deaths. Within three weeks, some 2,00,000 – 62% of the world’s population – were dead. This alarmed the scientists from across the globe as the species was already critically endangered in Central Asia. The reported symptoms were foaming at the mouth, diarrhoea and bloating. Initial research revealed it could be due to a disease. A 2018 report confirmed that the killar was a bacterium, Pasteurella multocida, that normally lives in the antelopes’ tonsils without causing any problems. It also revealed that unusually warm, moist weather may have triggered the overgrowth of the bacteria, which subsequently found its way into the antelopes’ tissues and bloodstream, causing haemorrhagic septicaemia or  fatal blood poisoning. Researchers say there is a high chance of the same thing happening again, given the climate change predictions for the region.

Similar die-offs were reported in 2010 and 1988. They were also linked to Pasteurella multocida. Today, roughly 50,000 saigas are thought to remain in the wild, according to the World Wildlife Fund.

 

Picture Credit : Google

Emphysema is a type of COPD (chronic obstructive pulmonary disease). COPD is a group of lung diseases that make it hard to breathe and get worse over time. The other main type of COPD is chronic bronchitis. Most people with COPD have both emphysema and chronic bronchitis, but how severe each type is can be different from person to person.

Emphysema affects the air sacs in your lungs. Normally, these sacs are elastic or stretchy. When you breathe in, each air sac fills up with air, like a small balloon. When you breathe out, the air sacs deflate, and the air goes out.

In emphysema, the walls between many of the air sacs in the lungs are damaged. This causes the air sacs to lose their shape and become floppy. The damage also can destroy the walls of the air sacs, leading to fewer and larger air sacs instead of many tiny ones. This makes it harder for your lungs to move oxygen in and carbon dioxide out of your body.

The cause of emphysema is usually long-term exposure to irritants that damage your lungs and the airways. In the United States, cigarette smoke is the main cause. Pipe, cigar, and other types of tobacco smoke can also cause emphysema, especially if you inhale them.

Exposure to other inhaled irritants can contribute to emphysema. These include secondhand smoke, air pollution, and chemical fumes or dusts from the environment or workplace.

Rarely, a genetic condition called alpha-1 antitrypsin deficiency can play a role in causing emphysema.

 

Picture Credit : Google