Buzz
A zoonosis refers to any disease that is transmitted from animals to humans. With over 850 known zoonoses, many of which are rarely contracted by humans, there are likely many more we are unaware of. Apart from the fourth entry on this list, these diseases are fairly obscure and, though uncommon, still infect hundreds or thousands of people each year. Each entry includes a quick overview of symptoms, risks, and treatments, along with some interesting facts about the pathogens involved.
10. Cat Scratch Disease
As the name implies, cats are the primary carriers of Cat Scratch Disease. This illness is spread through scratches or bites, with symptoms such as painful swelling of nearby lymph nodes and the appearance of papules, typically within one to two weeks after infection, though they can take up to eight weeks to show. Most cases resolve without medical treatment, but those with weakened immune systems, such as children and individuals with HIV, may need treatment to avoid complications like abscesses, pneumonia, or even coma.
9. Barmah Forest Virus
Found exclusively in Australia, Barmah Forest virus is a mosquito-borne pathogen that, while non-fatal, is closely related to the more widespread Ross River virus. Most people infected with Barmah Forest virus show no symptoms, but in those who do, the virus typically appears within two weeks with symptoms such as mild fever, headaches, fatigue, rashes, and painful swelling, particularly in the wrists and ankles. All symptoms, except for arthritis which may last up to six months or longer, usually resolve on their own in a couple of weeks. Though generally harmless, Barmah Forest virus can cause severe complications like Guillain–Barré syndrome or kidney inflammation in vulnerable individuals, both of which can be life-threatening.
8. Orf
Typically transmitted by sheep, Orf is contracted when the virus enters the body through cuts or abrasions in the skin. If standard wound care practices are followed, medical intervention is generally not required as the disease does not present significant complications. The primary symptoms of Orf are red papules or lesions at the site of the infection.
7. Bang’s Disease
With varying infection rates around the globe, Bang’s disease, also known as brucellosis, is a bacterial infection often spread through the consumption of unpasteurized milk or contaminated meat from infected cattle, sheep, pigs, or goats. It can also be contracted through open cuts that come into contact with the bodily fluids of an infected animal. Symptoms typically appear within a month and include flu-like signs such as fever, headaches, back and joint pain, and fatigue. If left untreated, Bang’s disease can cause severe complications, including heart infections, liver abscesses, and potentially death, as well as prolonged symptoms resembling chronic fatigue syndrome. In pregnant women, the disease can also result in miscarriages and birth defects.
6. Cryptosporidiosis
Unlike many diseases on this list, cryptosporidiosis can be transmitted not only from animals to humans but also from human to human. All infections occur due to the consumption of contaminated food or water. With an incubation period of up to ten days, the cryptosporidiosis parasite resides in the intestines of its host, causing acute symptoms in most cases that can last up to two weeks. These symptoms include stomach cramps, vomiting, nausea, fever, and dehydration. Treatments typically address the symptoms rather than the parasite itself, and as long as hydration is maintained, serious complications are rare. However, in individuals with a weakened immune system, hospitalization may be required to prevent death from chronic dehydration.
5. Toxocariasis
Toxocariasis is a parasitic infection contracted through contact with the contaminated feces of dogs, cats, and foxes. The eggs of the parasite can remain dormant within a host for up to two years before hatching. Once the larvae hatch, they typically settle in the intestines, causing mild symptoms such as headaches, coughing, stomach cramps, and a high fever if the parasite moves to other organs. In rare instances, the parasite may infect the eyes, leading to blurry vision and severe irritation, which if left untreated can result in permanent blindness.
4. Rabies
Perhaps the most well-known disease on this list, rabies has become especially notable today because it’s no longer seen as an automatic death sentence. Typically contracted through bites or cuts from infected animals, rabies has an unpredictable incubation period followed by rapid onset of severe neurological symptoms, ultimately leading to death as the virus disrupts brain function. However, in recent years, the 'Milwaukee Protocol' has garnered attention for successfully saving about 8% of unvaccinated patients it’s been applied to. While this figure may seem low, it’s significant compared to the virus's previous 100% mortality rate. The Milwaukee Protocol involves placing the rabies patient in a drug-induced coma and administering high doses of antivirals. While the exact mechanism remains unclear, it is believed that this process helps prevent brain dysfunction and gives the immune system more time to fight the virus.
3. Q Fever
Q Fever is considered one of the most infectious agents known to humans, with a single bacterium potentially capable of infecting the entire human population. While human-to-human transmission is rare (mostly via sexual contact), the disease is more commonly spread from livestock and domestic mammals through contact with their bodily fluids, including milk, feces, and semen (Q Fever is prevalent among zoosexuals and zoophiles). Symptoms typically appear within three weeks and include high fever, photophobia, severe headaches, and excessive sweating. Despite the high risk of complications, such as fatal pneumonia and hepatitis, prompt treatment with potent antibiotics results in a survival rate of over 90%. Treatment often needs to be extended for months, or even years, to fully eradicate the bacteria and prevent relapse. Worldwide, fewer than a thousand Q Fever cases are reported annually, and the bacterium is unlikely to mutate into something more dangerous. Nevertheless, Q Fever is classified as a Class B bioterror agent due to its highly infectious and incapacitating nature.
Honorable Mentions: Anthrax, Avian Flu, Bovine TB, Cholera, Cowpox, Creutzfeldt-Jakob disease, Dengue fever, Ebola, HIV, Plague, Salmonellosis, SARS (Debatable), Streptococcus Suis, Swine Flu, Typhus, West Nile Virus, Yellow Fever, Leprosy.
2. Black Fever
Black fever, the most severe form of leishmaniasis, is a parasitic disease transmitted by female sand fly bites in tropical and temperate regions worldwide. It infects up to half a million people each year, causing an estimated 50,000 deaths. Known as the deadliest human parasite after malaria, black fever has a 100% mortality rate if left untreated. Its symptoms closely resemble those of malaria, often resulting in fatal misdiagnosis. Infected individuals experience high fever, skin darkening, ulcers, weakness, fatigue, anemia, and enlargement of the spleen and liver. Without treatment, the disease attacks the immune system, leaving the body vulnerable to secondary infections, many of which can lead to pneumonia and death.
1. Pahvant Valley Plague
The Pahvant Valley Plague, commonly known as tularemia, is a dangerous bacterial disease native to North America. It is most frequently transmitted from rabbits to humans by ticks and lice. The infection can also spread through contaminated food or water or by handling the bodies of infected animals. Symptoms appear quickly, typically within three to five days after exposure, and can include fever, severe headaches, extreme weakness, fatigue, diarrhea, swollen joints, chills, inflamed lymph nodes and eyes, and ulcers in the mouth or on the skin. Tularemia is a serious condition that demands urgent antibiotic treatment to prevent potentially fatal complications like dehydration, pneumonia, or suffocation caused by respiratory failure.
