Why is Leptospirosis so difficult to catch?

Why is Leptospirosis so difficult to catch?

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I was on a small mammals training course and the professor was warning of the dangers of Leptospirosis. Apparently 5-40% of Rats have it and an unknown proportion of other animals. The warning sheet they handed out listed farmers, gardeners, etc as 'at risk' groups. I looked it up on the NHS website out of interest but it said there were only about 25 cases a year in the UK, even of the mild form.

I understand that it dies when it's dried out, but still, in notoriously rainy Britain, I can't seem to make sense of the numbers. There are at least half a million farmers in our country, probably a similar amount of gardeners, at least several thousand homeless and poverty stricken who must live in very close proximity to the huge urban Rat population, not to mention the potential for rodents to get into domestic water tanks. In rainy weather everything can stay wet for days. Also, if I remember rightly, an Olympic athlete recently died from it, so it obviously doesn't require a weak physiology to get in.

So, the question is, given what seems to me to be a massive prevalence (40% of all Rats), vast contact opportunities (all land workers during spells of wet weather), and seemingly a tough little organism (can kill an Olympic athlete), why is it so rare (25 cases in 70,000,000 people)?

Leptospirosis: What you need to know

Leptospirosis is a relatively rare bacterial infection that affects people and animals. It can pass from animals to humans when an unhealed break in the skin comes in contact with water or soil where animal urine is present.

Several species of the Leptospira genus of bacteria cause leptospirosis. It can progress to conditions such as Weil’s disease or meningitis, which can be fatal.

The condition does not usually pass from one person to another.

The bacteria can enter the body through open wounds, the eyes, or mucous membranes. Animals that transmit the infection to humans include rats, skunks, opossums, foxes, and raccoons.

Leptospirosis is more common in tropical areas, where the World Health Organization (WHO) estimate that it affects 10 or more people in every 100,000 each year.

In temperate climates, it probably affects between 0.1 and 1 per 100,000 people. In an epidemic, it can affect 100 or more in every 100,000 people.

People traveling to tropical areas have a greater risk of exposure.

Share on Pinterest Leptospirosis is a bacterial infection.

For mild cases, the doctor may prescribe antibiotics, such as doxycycline or penicillin.

Patients with severe leptospirosis will need to spend time in the hospital. They will receive antibiotics intravenously.

Depending on which organs leptospirosis affects, the individual may need a ventilator to help them breathe.

If it affects the kidneys, dialysis may be necessary.

Intravenous fluids can provide hydration and essential nutrients.

Hospital stays may range from a few weeks to several months. This mostly depends on how the patient responds to antibiotic treatment, and how severely the infection damages their organs.

During pregnancy, leptospirosis can affect the fetus. Anyone who has the infection during pregnancy will need to spend time in the hospital for monitoring.

The signs and symptoms of leptospirosis usually appear suddenly, about 5 to 14 days after infection. However, the incubation period can range from 2 to 30 days, according to the CDC.

Mild leptospirosis

Signs and symptoms of mild leptospirosis include :

  • a fever and chills
  • coughing , vomiting, or both
  • muscle pain, particularly lower back and calves
  • a rash
  • red and irritated eyes

Most people recover within a week without treatment, but around 10 percent go on to develop severe leptospirosis.

Severe leptospirosis

Signs and symptoms of severe leptospirosis will appear a few days after mild leptospirosis symptoms have disappeared.

Symptoms depend on which vital organs are involved. It can lead to kidney or liver failure, respiratory distress, and meningitis. These can be fatal.

The heart, liver, and kidneys

If leptospirosis affects the heart, liver, and kidneys, the person will experience:

Without treatment, this can lead to life-threatening kidney failure.

If it affects the brain or spinal cord, meningitis, encephalitis, or both may develop.

Meningitis is an infection of the membrane covering the brain and spinal cord, while encephalitis refers to infection of brain tissue. Both conditions have similar signs and symptoms.

  • confusion or disorientation
  • drowsiness
  • fits or seizures
  • high fever
  • nausea
  • photophobia, or sensitivity to light
  • problems with physical movements
  • stiff neck
  • inability to speak
  • vomiting
  • aggressive or unusual behavior

Untreated meningitis or encephalitis can result in serious brain damage, and it may be life-threatening.

If it affects the lungs, the person cannot breathe.

Signs and symptoms include:

In severe cases, there may be so much blood that the person suffocates.

Early-stage, mild leptospirosis is hard to diagnose, because the symptoms can resemble those of flu and other common infections.

If a physician suspects severe leptospirosis, the patient may undergo specific diagnostic tests . Various tests are available. In some cases, tests may need repeating to confirm the result.

The doctor will ask about any recent travel, especially to areas where leptospirosis is common.

They may ask if the person:

  • has been swimming in a lake, pond, canal, or river
  • has had contact with any activities that occurred in a slaughterhouse, on a farm, or relating to animal care
  • may have had contact with animal urine or blood

A number of blood and urine tests can confirm or rule out leptospirosis.

In the United States, leptospirosis is a notifiable disease . The doctor must inform the relevant health authorities if a person’s diagnosis confirms an infection.

There are two main types of leptospirosis.

Mild leptospirosis: This accounts for 90 percent of cases. Symptoms include muscle pain, chills, and possibly a headache.

Severe leptospirosis: Between 5 and 15 percent of cases can progress to severe leptospirosis. Organ failure, internal hemorrhaging, and death can result if the bacterium infects the liver, kidneys, and other major organs.

The Centers for Disease Control and Prevention (CDC) puts the fatality rate between 5 and 15 percent among those with severe illness.

With effective and timely treatment, leptospirosis is less likely to become severe.

Those more likely to develop severe leptospirosis tend to be those who are already sick, for example, with pneumonia, those under the age of 5 years, and those in older age.

Who is at risk?

Leptospirosis is more common in a tropical climate, but it may also occur in the poorer parts of large cities in developing nations that are not in tropical areas.

The risk is higher at times of excessive rainfall and flooding, according to the WHO.

The bacterium thrives in hot and humid environments. It tends to be sporadic rather than constantly present.

Leptospirosis is more likely to occur in:

  • South and Southeast Asia
  • Australia
  • the Caribbean and Central America
  • the Andes and tropical Latin America
  • East Sub-Saharan Africa

Tourist hotspots where leptospirosis sometimes occurs include New Zealand, Australia, Hawaii, and Barbados.

Flooding increases the risk of an outbreak. If climate change leads to more cases of flooding around the world, leptospirosis may become more common.

Leptospirosis in the United States

Around 100 to 150 cases occur each year in the U.S., mostly in Puerto Rico and Hawaii, according to the CDC. The largest number of cases was in 1998, when 775 people were exposed.

In countries such as the U.S., with a developed infrastructure, those most at risk are:

  • sewage workers
  • farm and agricultural workers who have regular contact with animals or infected water or soil
  • pet shop employees and veterinarians
  • abattoir workers and meat handlers
  • those involved in recreational water sports, such as sailing or canoeing
  • military personnel

Death rates in developed nations are much lower than in poorer countries, due to effective health care.

A number of measures can help reduce the risk of getting leptospirosis, especially among those whose leisure or work activities increase their risk.

Water sports: In non-tropical, developed nations, such as the U.S., the risk of leptospirosis is very small, and most people do not need to avoid doing water sports.

However, those who do watersports as part of a holiday adventure and those regularly swim in freshwater should take some precautions.

One is to make sure that any skin cuts are covered with a waterproof dressing.

This can protect against a range of infections, including hepatitis A and giardiasis.

After swimming in fresh water, it is a good idea to shower thoroughly.

Workplace exposure: Those who work with animals or potentially contaminated water or soil should wear protective clothing and comply with local or national rules and regulations.

They may need to wear gloves, masks, boots, and goggles.

Travel and tourism: People who travel to areas where leptospirosis is common should take the following steps:

  • Avoid swimming in fresh water.
  • Drink only water that is boiled or from a sealed bottle.
  • Clean and cover any skin wounds with a waterproof dressing.

Disaster response: Emergency workers or military personnel in disaster zones might have to take antibiotics as a precautionary measure.

Other tips

Other tips for avoiding leptospirosis include: where:

  • controlling pests, especially rodents
  • washing hands with soap and water after handling animals and animal products
  • avoiding touching dead animals with bare hands
  • cleaning all wounds as soon as possible and covering them with waterproof dressings
  • wearing protective clothing at work, if appropriate
  • avoiding wading, swimming, or other contact with rivers, streams, and lake water, especially after flooding, or shower at once after exposure
  • avoid contact with or consuming anything that has been in contact with flood water
  • avoiding drinking water from rivers and lakes unless it has been boiled or chemically treated
  • ensuring that dogs have a vaccination against leptospirosis

People can become infected through:

  • drinking contaminated water
  • unhealed cuts or wounds that come into contact with contaminated water or soil
  • the eyes, nose, or mouth coming into contact with contaminated water or soil
  • less commonly, contact with the blood of an infected animal

Infection rarely passes between humans, but this can sometimes happen during sexual intercourse or breastfeeding.

The Leptospira bacteria can exist in raccoons, bats, sheep, dogs, mice, rats, horses, cattle, buffaloes, and pigs.

The bacteria inhabit the animals’ kidneys and are expelled through urination, infecting the soil or water supplies.

Squirrel Diseases and Health Risks

NEED LOCAL HELP? We are wildlife removal professionals servicing 95% of the USA. Click here to hire our local squirrel removal expert in your home town. Updated 2021. But read the below advice first!

Are Squirrels A Health Risk To Humans?
Contrary to popular belief squirrels do not pose much of a health risk to humans. Anecdotal evidence may suggest that humans can catch rabies from squirrels, but, this is not confirmed by any reputable research. One of the ways squirrels may be a health risk is because of their droppings. In common with other rodents squirrels take a spray approach with both their feces and urine which may pose the risk of salmonella infection to anyone coming into contact with it. Once you have successfully dealt with your squirrel infestation it is essential that you undertake a deep clean of the whole area used by the rodents - this may also involve replacing any insulation materials.

The primary squirrel health risk is linked to ticks and fleas which squirrels tend to be infested with. Ticks carry the danger of tick fever and, once carried into your home by squirrels, may also infest your household pets. Fleas are also associated with squirrels and may also take up residence in your family pet - and once a flea or tick infestation has begun it is notoriously difficult to get rid of as these microscopic insects take up residence in carpets, soft furnishings and furniture.

Although any warm-blooded mammal (that's all mammals, by the way) can get rabies, some animals just aren't really very susceptible, nor are they common vectors of the disease (likely to spread it). Squirrels are such an animal. They don't really get rabies much, and there are no known cases of rabies transmission to people or pets. Read more about Do all squirrels have rabies? You can also read about Do squirrels bite?

Recognizing Squirrel Poop Types
Some people have said that having squirrels in the attic cannot be such a horrible problem. While there are pests that can cause more damage, you should not minimize the potential risks that squirrels can have on you and your family. Of course there are risks to the actual structure of your home, and there are also health risks. Most people would think that the main health risk from squirrels is rabies, but the truth is that the worst problems that you can have will have to do with their feces. So how do you recognize squirrel poop types?

Recognizing the poop is important because it lets you know which traps to use. The most common squirrels that can cause you a problem are the red and the gray squirrel. The main difference between their poops is the size they will both leave droppings that look to be the same shape (about the shape of rice). You recognize the different squirrel poop types because the gray squirrel is a bit larger than the red squirrel. That means that their poop is longer. The Flying squirrel's dropping are pretty close to the grey one's and they will all have a look that is pretty similar to wild rice.

What Can You Get With Squirrel Dung?
Squirrel droppings can be a source of Leptospirosis and salmonella. Leptospirosis is a bacterial infection which can manifest as a mild flu- like illness characterized by headache, aches and pains along with chills. This mild form of the disease is the most common. However if the condition becomes more serious then life threatening symptoms may develop including organ failure and internal bleeding. Mild doses of leptospiros can be treated with antibiotics but more severe cases my require hospital admission. This infection is a typical incidence of what you can get with squirrel dung.

Salmonella is a well known disease commonly defined as food poisoning it will present with sickness and diarrhea and in mild doses may be no more than an inconvenience however, as with letptospirosis live threatening complications can occur especially in the elderly or very young. It is possible that contracting salmonella my also require hospitalisaton. The best possible way to avoid any risk of infection from any animal dung is to ensure that the highest level of hygiene id maintained at all times. It is easy to avoid the risk of infection by a strict regime of hand washing. There as been some suggestion that so-called ‘mad cow disease' has been contracted from squirrels but the evidence is anecdotal at best.

Worried About Squirrel Smell Removal? Dead Animals Can Be Dangerous
If you see a dead squirrel in your yard and you have no idea how it died, you may be safer if you do not touch it yourself. You can call the "County Department of Public Works" or "County Department of Animal Care and Control" and they will send someone to your house to pick up the cadaver. Your phone book is usually the best guide on whom to call for this purpose.

In some instances, you may not see the animal but you will surely be able to smell it if it is close enough. If this happens on a weekend and you cannot reach anyone from your county to pick up the animal, you may have to do it yourself. You definitely want to be rid of it sooner than the next work day if you have children and pets roaming on your property or if you have guests over for a pic-nic in your backyard. Since you don't know what killed the squirrel, you have to assume it carries a contagious disease. Wear protective clothing and goggles if you remove it yourself. Pick it up with either a shovel or some extension, like those long-handled grippers so that you don't touch it. Then double bag it in plastic bags and put it into an empty metal trash can until the county picks it up.

Is There A Squirrel Disease Masks Can Prevent
The ‘pox virus' which is carried by the grey squirrel has decimated the indigenous population of red squirrels. The squirrel pox virus whilst deadly for red squirrels is harmless to greys. This means that as the grey squirrels pass the pox virus around then they are also responsible for wiping out the red squirrel population - and may in fact completely replace that population within 15 years. There is currently no other solution to this problem other than trapping and killing the grey squirrels in order to protect the red population until a vaccine is developed.

Squirrels which eat at feeding stations have been found to contract coccidiosis - a parasite which lives in the gut, this is due to bad hygiene around the feeders, therefore if you have a squirrel feeder and are hoping to protect the endangered red squirrel population the feeder needs to be regularly cleaned. Whilst squirrels often carry a variety of parasites generally they cause little harm or discomfort to the animal, however both squirrel pox virus and coccidiosis have severe and usually fatal effects. Generally speaking, those diseases and parasites which are a threat to squirrels pose no such threat to humans. However if you have to remove any dead animal or fecal matter then it is wise to do so carefully and hygienically in order to avoid any possible risk of infection. Click here for more information about squirrel feces in an attic or home. Click here for more information about squirrel urine and proper cleanup. Read About Squirrels for biology info.

Go back to the Squirrels in the Attic home page.

NEED SQUIRREL REMOVAL HELP? We service over 150 USA cities. click gere to hire us in your home town. Updated 2021.

Editors' Summary

Humans catch many diseases from animals—so-called zoonotic infections. Often, these occur in limited regions of the world. However, one—leptospirosis—occurs in temperate and tropical climates, and in urban and rural settings, making it the most widespread zoonotic disease. Leptospirosis is caused by Leptospira, a large group of closely related spiral-shaped bacteria that live in both domestic animals (for example, cattle) and wild animals (particularly rats). Millions of humans become infected each year with leptospires through close contact with water, food, or soil contaminated with the urine of infected animals—swimming or wading in contaminated water is particularly hazardous. Some infected people have no symptoms others develop a flu-like disease that clears up within a few days. However, in 5%–10% of infected people, the disease progresses to a second, sometimes fatal phase. This is usually characterized by jaundice, kidney problems, and an enlarged spleen (it's then called Weil disease) but can also involve the lungs (pulmonary leptospirosis). Leptospirosis can be successfully treated with antibiotics if treatment is started soon after infection.

In a recent study in the Peruvian Amazon, half of the people visiting urban hospitals and rural health posts with acute fever had antibodies in their blood to Leptospira, suggesting that they had acute leptospirosis. However, only patients living in urban areas developed pulmonary leptospirosis. In this study, the researchers tested the hypothesis that this pattern arose because more virulent types of Leptospira were present at higher levels in urban environmental surface water than in rural water sources.

Between June 2003 and March 2004, the researchers isolated strains of Leptospira from patients with acute fever who visited a hospital in the town of Iquitos or clinics in nearby villages. Early in 2004, they also collected a large number of different water samples from an urban slum in Iquitos and from a nearby rural community. They measured the concentrations of Leptospira in these samples by using a molecular technique called real-time PCR (polymerase chain reaction) to detect and quantify a type of RNA found only in disease-causing Leptospira. They also identified which specific Leptospira were present in the water samples and the patient samples by sequencing this RNA. The researchers found that leptospires were present in both urban and rural water samples (particularly in samples from gutters and puddles in the urban slum's market area) but that their concentration in the positive water samples from the urban sites was 20 times that in the positive samples from the rural sites. Furthermore, the distribution of different Leptospira types isolated from the patients mirrored that of the bacteria in the local environment. So, one particular type of Leptospira interrogans known as icterohaemorrhagiae—the leptospire most commonly associated with severe leptospirosis in the patients—was found more often in the urban water samples than in the rural ones. Finally, the researchers discovered a new group of Leptospira in the rural environment. This group may contain one or several new species of Leptospira but whether any of them causes human disease is unknown.

These results support the researchers' hypothesis that pulmonary leptospirosis in urban areas of the Peruvian Amazon is associated with high environmental levels of specific disease-causing leptospires. The researchers were able to discover this link only by using molecular techniques—this sort of study is impossible with traditional bacteriological techniques because Leptospira are hard to grow in the laboratory and cannot be isolated efficiently from environmental water sources. Different types can't be identified using a microscope. The researchers' findings need to be validated in other settings, but they suggest that environmental interventions such as reducing sources of standing water and clearing away garbage in urban areas might reduce the number of cases of severe leptospirosis. The distribution of different Leptospira types also suggests that whereas rats may be the main disease reservoir in towns, cattle, pigs, and bats may be more important in rural settings in Peru and presumably elsewhere. Overall, this new information, together with the availability of molecular methods for rapid clinical diagnosis and environmental risk assessment, should aid attempts to control leptospirosis around the world.

Please access these Web sites via the online version of this summary at

  • US Centers for Disease Control and Prevention, information for patients and professionals on leptospirosis
  • The Leptospirosis Information Center, information and advice on human leptospirosis for the public and medical professionals
  • MedlinePlus encyclopedia entry on leptospirosis
  • NHS Direct Online, patient information on leptospirosis from the UK National Health Service online encyclopedia (note: Wikipedia is a free online encyclopedia that anyone can edit)

Symptoms of Leptospirosis in Dogs

These are the symptoms you might see in dogs infected with leptospirosis:

Sore muscles reluctance to move

Stiffness in muscles and legs stiff gait

Increased thirst and urination—may be indicative of chronic renal (kidney) failure, progressing to an inability to urinate

Vomiting, possibly with blood

Diarrhea, with or without blood

Dark red-speckled gums (petechiae)

Yellow skin and/or whites of eyes (anemic symptoms)

Difficulty breathing, fast breathing, irregular pulse

Swelling of the mucous membrane

Mild swelling of the lymph nodes

Taking Action at The Marine Mammal Center

Each year, The Marine Mammal Center’s specially trained teams rescue marine mammals exhibiting signs of unfortunate run-ins with our trash. Typically, California sea lions are rescued with plastic netting, packing straps and other pieces of trash caught around their neck and face. Other animals have been rescued with plastic trash in their stomachs, such as plastic bags and balloons.

The Center’s Whale Entanglement Response and Prevention program focuses on responding to large whales in distress, often due to entanglements in fishing gear, as well as working toward solutions by collaborating with the fishing industry and other important stakeholders.

How to Get Rid of Rats

Depending on your perspective, rats are either the superheroes or supervillains of the animal world. Equipped with incredible survival skills and high intelligence, rats often survive a range of difficult environmental conditions and even all-out human efforts to kill them.

Domesticated rats can make for low-maintenance pets, as they bond deeply with their owners and exhibit quirky personality traits. But wild rats, like the Norway and brown rats found throughout many major cities, are often a public health nuisance.

The Centers for Disease Control indicate that rats can spread dozens of diseases around the globe. You can get sick from rodents directly if they bite you (which happens about 15,000 times per year in the U.S.), or if you touch their urine, feces or saliva, resulting in nasty infections like salmonellosis, Hantavirus, leptospirosis, tularemia, lassa fever or even plague. Just as bad, you can become very ill if ticks, fleas, or mites feed on an infected rat and then bite you, resulting in diseases like Colorado tick fever, Lyme disease, West Nile virus, typhus, among others.

Rat Superpowers

Rats often scamper through restaurants at night, searching for food, spreading bacteria and droppings in revolting ways. In rare situations, they'll even attack humans, biting them repeatedly if they can't defend themselves. And because their teeth grow continuously, at a rate of up to 5 inches (12.7 centimeters) per year, rats gnaw on just about anything to file down their teeth, from cinder blocks to metal sheeting to the electrical wiring in homes and vehicles, causing major damage and potential fire hazards.

Rats are adept climbers they can squeeze through holes the size of U.S. quarter, survive falls of up to 50 feet (15 meters), and swim for days without drowning, just a few reasons that attempting to control their populations is often downright exasperating. In 2017, for example, New York City – a notorious haven for these large rodents – launched a $32-million war on rats. In spite of those efforts, and those in other cities, rat populations continue to explode, partially because climate change is leading to longer breeding seasons, allowing females to give birth to extra litters.

Mike Deutsch is a medical entomologist and technical director of Arrow Exterminating Company in Lynbrook, New York. He says via email that rats make their presence known with "fecal droppings, urine stains, gnaw marks on materials and the presence of live and dead rodents on or in the structure. Rats have oily fur and leave oily stains on surfaces that they frequently use." Many homeowners notice behavioral changes in their pets, too, as dogs and cats may stare at walls or exhibit excitement when they detect rodents that humans cannot.

There's no "magic bullet" for rat control, says Deutsch. Rat exterminators lean on a philosophy called Integrated Pest Management (or IPM), which requires them to weigh mechanical, physical, cultural and chemical control options in their efforts to stamp out unwanted intruders. Doing so is easier said than done.

"Rat abatement is very challenging," says Deutsch. "You must understand the biology, behavior and ecology of these animals to effectively eliminate them from a structure." Rats thrive in human filth, particularly in places with high population densities. That's why cities riddled with easily-accessible trash and aging, holey buildings, like New York City, are particularly active rat hotspots.

Getting Rid of Rats

That said, there are some tactics that you can use to address the problem. The first step in stopping rats is to make their habitat less desirable for feeding and nesting. Rats typically live out their lives no more than 400 feet (122 meters) from a primary food source. So, if you can reduce a rat's ability to find food, it is less likely to pay you uninvited visits.

1. Pick Up All Food-related Trash in the Vicinity of Your Home

When you to place rubbish out for trash collection, use rat-resistant containers, and keep all compost and trash as far from your home as possible. Store all other food sources, like birdseed or grass seed or pet foods, in rat-proof containers, too. Pick up and discard dog droppings in your yard daily. Trim tall grass and get rid of wood piles and other junk around your property, as these items often create suitable rat habitat. Keep outdoor grilling areas clean and free of food debris.

2. Keep Rats From Getting into Structures

That means sealing up gaps and holes, and using the right tools for the job, such as heavy-gauge screening or 1/4-inch (6-millimeter) hardware cloth. You can also use copper mesh, shoving it into those tight spaces that might tempt rat teeth. Finish this process with foam insulation and caulk. Make sure no tree branches or shrubs are touching your home, particularly near roof lines, because rats can climb foliage and then find ways into the structure.

3. Resort to Rat Traps

Non-lethal traps do work but leave you with the challenge of releasing the rats into a new area, where they may cause new misery for someone else. Rodenticides may work, but these poisons might take weeks to have any effect and often unintentionally kill other animals.

Old-school snap traps may be your best bet. You can purchase rat traps at your local hardware or big box store and then bait them. Contrary to popular belief, rodents don't particularly like cheese, and actually prefer peanut butter. Put a dollop of peanut butter the size of a pea on the rat traps. If your problem is in your kitchen, set up several traps under the sink or next to the wall. When you place the trap near a wall, create a T-shape with the bait next to the wall, because rats prefer to run right next to walls rather than out in the open. If you're setting the traps in the attic or basement, place the traps where you have found rat droppings.

It may take several days to catch the rat, and you may have to adjust your strategies several times in order to complete the job. If all else fails and rats are making your life difficult, call in a professional in order to make sure the job is done thoroughly.

In the wild, rats typically die at an age of 2 to 3 years old. But they can start breeding just three months after they're born, and they can have six litters of roughly 12 pups each year, meaning that in 12 months they could have about 2,000 descendants. Put another way, during their three-year lifespan, 6,000 babies can emerge from a single pair of breeding rats.

The Mongoose Comes to the Island

In the mid-1800s, sugar plantation profits were sagging. Plantation owners on Jamaica knew why, or least thought they did: rats.

They sought the perfect rat trap: something that would eliminate great numbers of the pests, cheaply and with little oversight.

In India, British colonialists witnessed a small carnivore eating rats quite effectively. The small Indian mongoose (Herpestes javanicus) tolerated humanity and a wide range of habitats and had a seemingly voracious appetite.

In the early 1870s, plantation owners brought nine small Indian mongooses to Jamaica. They were released. Plantation profits went up. The mongoose is an agricultural hero! Just think what it could do for other islands!

Important point here: Correlation does not imply causation. This will not be the last time this phrase plays a role in this story.

Changing management of plantations likely played a bigger role in increased profits. Rats, after all, are nocturnal, and mongoose, diurnal. Rats are also crafty – able to adapt quickly to predators.

No matter. Prevailing opinion had already proclaimed the mongoose a winner. The succeeding generations of those initial nine mongooses stormed the world – being spread to other Caribbean and Hawaiian islands.

Buzz Hoagland has handled thousands of mongoose in the course of his research. Photo courtesy Buzz Hoagland

9. Ruth Bader Ginsburg beat the odds and survived pancreatic cancer.

Ten years after she recovered from colon cancer, Ruth Bader Ginsburg received bad news following a routine check-up in 2009: She had pancreatic cancer. Fortunately, surgeons were able to remove the tumor, and at 85 years old (and counting), Ginsburg is now the oldest Justice on the U.S. Supreme Court. However, most people with pancreatic cancer aren’t so lucky. Although it’s less prevalent than skin, breast, and prostate cancers, it’s one of the deadliest. Just 8 percent of pancreatic cancer patients in the U.S. live longer than five years, according to the American Cancer Society.

James Cleary, an oncologist at the Dana-Farber Cancer Institute in Boston, says it’s very hard to catch in the early stages. “The reason pancreatic cancer can be so difficult to catch is number one, it’s a fast-moving cancer and can grow very rapidly,” he tells Mental Floss. “And number two, it can grow in a spot where you don’t get any symptoms until it’s too late.” In some cases, the cancer may start in the pancreas and spread to the liver or lining of the abdomen without any symptoms showing up.

Reducing the Risk

While it can be difficult to stop opossums from traveling through your yard, many strategies can help dissuade them from frequenting your land. Do not feed dogs outside if possible if you must do so, be sure to remove any uneaten food promptly, and keep stored food locked tight. Opossums avoid traversing open expanses if possible, so try to remove all forms of cover they may use. Understand that the urine, feces and saliva of opossums can carry pathogens, so it is wise to discourage their presence.