Cat bites are usually considered as minor injuries but can result in serious infection. Not all infections that can be obtained from exposure to a cat are transmitted through a cat bite, like plague.

Cat bites are bites inflicted upon humans, other cats, and other animals by the domestic cat. () Though uncommon, sometimes cat bites can lead to complications and very rarely, death.

Almost all spiders are venomous, but not all spider bites result in the injection of venom. Pain from non-venomous, so-called "dry bites" typically lasts for 5 to 60 minutes while pain from envenomating spider bites may last for longer than 24 hours. Bleeding also may occur with a bite. Signs of a bacterial infection due to a spider bite occur infrequently (0.9%).

A study of 750 definite spider bites in Australia indicated that 6% of spider bites cause significant effects, the vast majority of these being redback spider bites causing significant pain lasting more than 24 hours. Activation of the sympathetic nervous system can lead to sweating, high blood pressure and gooseflesh.

Most recluse spider bites are minor with little or no necrosis. However, a small number of bites produce necrotic skin lesions. First pain and tenderness at the site begin. The redness changes over two to three days to a bluish sinking patch of dead skin—the hallmark of necrosis. The wound heals slowly over months but usually completely. Rarely, bites may cause widespread symptoms, with occasional fatalities.

A spider bite, also known as arachnidism, is an injury resulting from the bite of a spider. The effects of most bites are not serious. Most bites result in mild symptoms around the area of the bite. Rarely they may produce a necrotic skin wound or severe pain.

Most spiders do not cause bites that are of importance. For a bite to be significant, substantial envenomation is required. Bites from the widow spiders involve a neurotoxic venom which produces a condition known as latrodectism. Symptoms may include: pain which may be at the bite or involve the chest and abdomen, sweating, muscle cramps and vomiting among others. Bites from the recluse spiders cause the condition loxoscelism, in which local necrosis of the surrounding skin and widespread breakdown of red blood cells may occur. Headaches, vomiting and a mild fever may also occur. Other spiders that can cause significant bites include: the Australian funnel-web spider and South American wandering spider.

Efforts to prevent bites include clearing clutter and the use of pesticides. Most spider bites are managed with supportive care such as nonsteroidal anti-inflammatory drugs (including ibuprofen) for pain and antihistamines for itchiness. Opioids may be used if the pain is severe. While an antivenom exists for black widow spider venom, it is associated with anaphylaxis and therefore not commonly used in the United States. Antivenom against funnel web spider venom improves outcomes. Surgery may be required to repair the area of injured skin from some recluse bites.

Spider bites may be overdiagnosed or misdiagnosed. In many reports of spider bites it is unclear if a spider bite actually occurred. Historically a number of conditions were attributed to spider bites. In the Middle Ages a condition claimed to arise from spider bites was tarantism, where people danced wildly. While necrosis has been attributed to the bites of a number of spiders, good evidence only supports this for recluse spiders.

The period between infection and the first symptoms (incubation period) is typically 1–3 months in humans. Incubation periods as short as four days and longer than six years have been documented, depending on the location and severity of the contaminated wound and the amount of virus introduced. Initial signs and symptoms of rabies are often nonspecific such as fever and headache. As rabies progresses and causes inflammation of the brain and/or meninges, signs and symptoms can include slight or partial paralysis, anxiety, insomnia, confusion, agitation, abnormal behavior, paranoia, terror, and hallucinations, progressing to delirium, and coma. The person may also have hydrophobia.

Death usually occurs 2 to 10 days after first symptoms. Survival is rare once symptoms have presented, even with the administration of proper and intensive care. Jeanna Giese, who in 2004 was the first patient treated with the Milwaukee protocol, became the first person ever recorded to have survived rabies without receiving successful post-exposure prophylaxis. An intention-to-treat analysis has since found this protocol has a survival rate of about 8%.

Symptoms vary on severity, from mild unnoticeable symptoms to more common symptoms like fever, rash, headache, achy muscle and joints, and conjunctivitis. Symptoms can last several days to weeks, but death resulting from this infection is rare.

Cryptosporidiosis is a parasitic disease that is transmitted through contaminated food or water from an infected person or animal. Cryptosporidiosis in cats is rare, but they can carry the protozoan without showing any signs of illness. Cryptosporidiosis can cause profuse, watery diarrhea with cramping, abdominal pain, and nausea in people. Illness in people is usually self-limiting and lasts only 2–4 days, but can become severe in people with weakened immune systems. Cryptosporidiosis (Cryptosporidium spp.) Cats transmit the protozoan through their feces. The symptoms in people weight loss and chronic diarrhea in high-risk patients. More than one species of this genus can be acquired by people. Dogs can also transmit this parasite.

Symptoms of illness are specific to the type of viral infection and vary on severity, based on the individuals infected.

Many species of arthropods (insects, arachnids and others) regularly or occasionally bite or sting human beings. Insect saliva contains anticoagulants and enzymes that cause local irritation and allergic reactions. Insect venoms can be delivered by their stingers, which often are modified ovipositors, or by their mouthparts. Insect, spider and scorpion venom can cause serious injury or death. Dipterans account for the majority of insect bites, while hymenopterans account for the majority of stings. Among arachnids spider bites are the most common. Arthropods bite or sting humans for a number of reasons including feeding or defense. Arthropods are major vectors of human disease, with the pathogens typically transmitted by bites.

Individual responses to bites vary, ranging from no visible effect (in about 20–70%), to small macular spots, to prominent wheals and bullae formations along with intense itching that may last several days. The bites often occur in a line. A central hemorrhagic spot may also occur due to the release of anticoagulants in the saliva.

Symptoms may not appear until some days after the bites have occurred. Reactions often become more brisk after multiple bites due to possible sensitization to the salivary proteins of the bed bug. The skin reaction usually occurs in the area of the bite which is most commonly the arms, shoulders and legs as they are more frequently exposed at night. Numerous bites may lead to an erythematous rash or urticaria.

Serious infestations and chronic attacks can cause anxiety, stress, and insomnia. Development of refractory delusional parasitosis is possible, as a person develops an overwhelming obsession with bed bugs.

Feline zoonosis are the viral, bacterial, fungal, protozoan, nematode and arthropod infections that can be transmitted to humans from the domesticated cat, "Felis catus". Some of these are diseases are reemerging and newly emerging infections or infestations caused by zoonotic pathogens transmitted by cats. In some instances, the cat can display symptoms of infection (these may differ from the symptoms in humans) and sometimes the cat remains asymptomatic. There can be serious illnesses and clinical manifestations in people who become infected. This is dependent on the immune status and age of the person. Those who live in close association with cats are more prone to these infections. But those that do not keep cats as pets are also able to acquire these infections because of the transmission can be from cat feces and the parasites that leave their bodies.

People can acquire cat-associated infections through bites, scratches or other direct contact of the skin or mucous membranes with the cat. This includes 'kissing' or letting the animal lick the mouth or nose. Mucous membranes are easily infected when the pathogen is in the mouth of the cat. Pathogens can also infect people when there is contact with animal saliva, urine and other body fluids or secretions, When fecal material is unintentionally ingested, infection can occur. Feline zooinosis can be acquired by a person by inhalation of aerosols or droplets coughed up by the cat.

In the United States, forty percent of homes have at least one cat. Some contagious infections such as campylobacteriosis and salmonellosis cause visible symptoms of the disease in cats. Other infections, such as cat scratch disease and toxoplasmosis, have no visible symptoms and are carried by apparently healthy cats.

The most common symptom of all snakebites is overwhelming fear, which contributes to other symptoms, including nausea and vomiting, diarrhea, vertigo, fainting, tachycardia, and cold, clammy skin. Television, literature, and folklore are in part responsible for the hype surrounding snakebites, and people may have unwarranted thoughts of imminent death.

Dry snakebites and those inflicted by a non-venomous species can still cause severe injury. There are several reasons for this: a snakebite may become infected, with the snake's saliva and fangs sometimes harboring pathogenic microbial organisms, including "Clostridium tetani". Infection is often reported with viper bites whose fangs are capable of deep puncture wounds. Bites may cause anaphylaxis in certain people.

Most snakebites, whether by a venomous snake or not, will have some type of local effect. There is minor pain and redness in over 90 percent of cases, although this varies depending on the site. Bites by vipers and some cobras may be extremely painful, with the local tissue sometimes becoming tender and severely swollen within five minutes. This area may also bleed and blister and can eventually lead to tissue necrosis. Other common initial symptoms of pit viper and viper bites include lethargy, bleeding, weakness, nausea, and vomiting. Symptoms may become more life-threatening over time, developing into hypotension, tachypnea, severe tachycardia, severe internal bleeding, altered sensorium, kidney failure, and respiratory failure.

Bites caused by some snakes, such as the kraits, coral snake, Mojave rattlesnake, and the speckled rattlesnake, reportedly cause little or no pain despite being serious potentially life-threatening injuries. Those bitten may also describe a "rubbery", "minty", or "metallic" taste if bitten by certain species of rattlesnake. Spitting cobras and rinkhalses can spit venom in a person's eyes. This results in immediate pain, ophthalmoparesis, and sometimes blindness.

Some Australian elapids and most viper envenomations will cause coagulopathy, sometimes so severe that a person may bleed spontaneously from the mouth, nose, and even old, seemingly healed wounds. Internal organs may bleed, including the brain and intestines and will cause ecchymosis (bruising) of the skin.

Venom emitted from elapids, including sea snakes, kraits, cobras, king cobra, mambas, and many Australian species, contain toxins which attack the nervous system, causing neurotoxicity. The person may present with strange disturbances to their vision, including blurriness. Paresthesia throughout the body, as well as difficulty in speaking and breathing, may be reported. Nervous system problems will cause a huge array of symptoms, and those provided here are not exhaustive. If not treated immediately they may die from respiratory failure.

Venom emitted from some types of cobras, almost all vipers and some sea snakes causes necrosis of muscle tissue. Muscle tissue will begin to die throughout the body, a condition known as rhabdomyolysis. Rhabdomyolysis can result in damage to the kidneys as a result of myoglobin accumulation in the renal tubules. This, coupled with hypotension, can lead to acute renal failure, and, if left untreated, eventually death.

The reaction to a sting is of three types. The normal reaction involves the area around the bite with redness, itchiness, and pain. A large local reaction occurs when the area of swelling is greater than 5 cm. Systemic reactions are when symptoms occur in areas besides that of the bites.

With insect stings a large local reaction may occur (an area of skin redness greater than 10 cm in size). It can last one to two days. It occurs in about 10% of those bitten.

Avian malaria is a parasitic disease of birds, caused by parasite species belonging to the genera "Plasmodium" and "Hemoproteus" (phylum Apicomplexa, class Haemosporidia, family Plasmoiidae). The disease is transmitted by a dipteran vector including mosquitoes in the case of "Plasmodium" parasites and biting midges for "Hemoproteus." The range of symptoms and effects of the parasite on its bird hosts is very wide, from asymptomatic cases to drastic population declines due to the disease, as is the case of the Hawaiian honeycreepers. The diversity of parasites is large, as it is estimated that there are approximately as many parasites as there are species of hosts. Co-speciation and host switching events have contributed to the broad range of hosts that these parasites can infect, causing avian malaria to be a widespread global disease, found everywhere except Antarctica.

A robovirus is a zoonotic virus that is transmitted by a rodent vector (i.e., "ro"dent "bo"rne).

Roboviruses mainly belong to the Arenaviridae and Hantaviridae family of viruses. Like arbovirus ("ar"thropod "bo"rne) and tibovirus ("ti"ck "bo"rne) the name refers to its method of transmission, known as its vector. This is distinguished from a clade, which groups around a common ancestor. Some scientists now refer to arbovirus and robovirus together with the term ArboRobo-virus.

Three stages of rabies are recognized in dogs and other animals.

1. The first stage is a one- to three-day period characterized by behavioral changes and is known as the prodromal stage.

2. The second stage is the excitative stage, which lasts three to four days. It is this stage that is often known as "furious rabies" due to the tendency of the affected animal to be hyperreactive to external stimuli and bite at anything near.

3. The third stage is the paralytic stage and is caused by damage to motor neurons. Incoordination is seen due to rear limb paralysis and drooling and difficulty swallowing is caused by paralysis of facial and throat muscles. This disables the victim's ability to swallow, which causes saliva to pour from the mouth also the reason bites are the most clear way for the infection to spread is because the virus is most concentrated in the throat and cheeks causing major contamination to saliva. Death is usually caused by respiratory arrest.

Hydrophobia ("fear of water") is the historic name for rabies. It refers to a set of symptoms in the later stages of an infection in which the person has difficulty swallowing, shows panic when presented with liquids to drink, and cannot quench his or her thirst. Any mammal infected with the virus may demonstrate hydrophobia.

Saliva production is greatly increased, and attempts to drink, or even the intention or suggestion of drinking, may cause excruciatingly painful spasms of the muscles in the throat and larynx. This can be attributed to the fact that the virus multiplies and assimilates in the salivary glands of the infected animal for the purpose of further transmission through biting. The ability to transmit the virus would decrease significantly if the infected individual could swallow saliva and water.

Hydrophobia is commonly associated with furious rabies, which affects 80% of rabies-infected people. The remaining 20% may experience a paralytic form of rabies that is marked by muscle weakness, loss of sensation, and paralysis; this form of rabies does not usually cause fear of water.

Avian malaria is most notably caused by Plasmodium relictum, a protist that infects birds in all parts of the world apart from Antarctica. There are several other species of "Plasmodium" that infect birds, such as "Plasmodium anasum" and "Plasmodium gallinaceum", but these are of less importance except, in occasional cases, for the poultry industry. The disease is found worldwide, with important exceptions. Usually, it does not kill birds. However, in areas where avian malaria is newly introduced, such as the islands of Hawaiʻi, it can be devastating to birds that have lost evolutionary resistance over time.

Feeding bites have characteristic patterns and symptoms, a function of the feeding habits of the offending pest and the chemistry of its saliva.

Animal trypanosomiasis, also known as nagana and nagana pest, or sleeping sickness, is a disease of vertebrates. The disease is caused by trypanosomes of several species in the genus "Trypanosoma" such as "Trypanosoma brucei". "Trypanosoma vivax" causes nagana mainly in West Africa, although it has spread to South America. The trypanosomes infect the blood of the vertebrate host, causing fever, weakness, and lethargy, which lead to weight loss and anemia; in some animals the disease is fatal unless treated. The trypanosomes are transmitted by tsetse flies.

An interesting feature is the remarkable tolerance to nagana pathology shown by some breeds of cattle, notably the N'Dama – a West African "Bos taurus" breed. This contrasts with the susceptibility shown by East African "Bos indicus" cattle such as the zebu.

A bite of "Latrodectus" may not inject any venom (known as a dry bite) and so no illness occurs. About 75% of "wet" bites will have localized pain and nothing more. If, however, there is a substantial dose, a bite can cause latrodectism. The main symptoms are generalized muscle pain, stomach cramps, nausea and vomiting.

Initially a pinprick or burning sensation can be felt when bitten by widow spiders. If there was enough venom injected, pain worsens over the next hour. The area will develop localized sweating and gooseflesh piloerection. The pain may spread and become generalized.

The typical duration is three to six days. Some people who do not receive antivenom may feel unwell, be weak, and have muscle pain for weeks.

Rabies is a viral zoonotic neuroinvasive disease which causes inflammation in the brain and is usually fatal. Rabies, caused by the rabies virus, primarily infects mammals. In the laboratory it has been found that birds can be infected, as well as cell cultures from birds, reptiles and insects. Animals with rabies suffer deterioration of the brain and tend to behave bizarrely and often aggressively, increasing the chances that they will bite another animal or a person and transmit the disease. Most cases of humans contracting the disease from infected animals are in developing nations. In 2010, an estimated 26,000 people died from rabies, down from 54,000 in 1990.

A tick infestation is a condition where a tick acts as an ectoparasite.

It is sometimes thought of as an animal disease. In humans, the primary concern from tick bites is often not the ectoparasitism itself, but the potential for the tick to transmit disease or tick paralysis. Still, in certain populations, it is possible for tick infestation to be clinically significant.

There is some evidence that "Ixodes ricinus" infected with "Borrelia burgdorferi" may become more efficient at infestation.

Home remedies (such as vaseline or matches) have been used in the past, but are not currently recommended.

Latrodectism is the illness caused by the bite of "Latrodectus" spiders (the black widow spider and related species). Pain, muscle rigidity, vomiting, and sweating are the symptoms of latrodectism. Contrary to popular conception, latrodectism is very rarely fatal to people though domestic cats have been known to die with convulsion and paralysis.

There are several spider species all named black widow: southern black widow spider ("L. mactans"), the European black widow ("L. tredecimguttatus"), Western black widow spider ("L. hesperus"), Northern black widow spider ("L. variolus"). Other "Latrodectus" that cause latrodectism are the Australian redback spider ("L. hasselti"), and the New Zealand katipo spider ("L. katipo"). Several other members of "Latrodectus" genus are not commonly associated with latrodectism including the cosmopolitan brown widow ("L. geometricus").