As is often the case, there are diseases/conditions with signs and symptoms that are similar to actinomycosis. As such, misdiagnoses can occur. Some examples include abscesses caused by grass seeds, woody tongue, bottle jaw, cancerous growths, and irritation caused by lodged objects.

The "Actinomyces" bacteria that cause lumpy jaw are always present in a healthy cattle's mouth. In order for infection to occur, there must be tissue damage, which is often caused by unusually rough feed that scratches the mouth of the animal or by contact with sharp objects, such as sticks or brambles. Given the mode of infection, lumpy jaw is not contagious.

Actinomycosis is primarily caused by any of several members of the bacterial genus "Actinomyces". These bacteria are generally anaerobes. In animals, they normally live in the small spaces between the teeth and gums, causing infection only when they can multiply freely in anoxic environments. An affected human often has recently had dental work, poor oral hygiene, periodontal disease, radiation therapy, or trauma (broken jaw) causing local tissue damage to the oral mucosa, all of which predispose the person to developing actinomycosis. "A. israelii" is a normal commensal species part of the microbiota species of the lower reproductive tract of women. They are also normal commensals among the gut flora of the caecum; thus, abdominal actinomycosis can occur following removal of the appendix. The three most common sites of infection are decayed teeth, the lungs, and the intestines. Actinomycosis does not occur in isolation from other bacteria. This infection depends on other bacteria (Gram-positive, Gram-negative, and cocci) to aid in invasion of tissue.

Disease incidence is greater in males between the ages of 20 and 60 years than in females. Before antibiotic treatments became available, the incidence in the Netherlands and Germany was one per 100,000 people/year. Incidence in the U.S. in the 1970s was one per 300,000 people/year, while in Germany in 1984, it was estimated to be one per 40,000 people/year. The use of intrauterine devices (IUDs) has increased incidence of genitourinary actinomycosis in females. Incidence of oral actinomycosis, which is harder to diagnose, has increased.

Actinobacillosis is a zoonotic disease caused by Actinobacillus.

It is more commonly associated with animals than with humans.

One of the most common forms seen by veterinarians is mouth actinobacillosis of cattle, due to "Actinobacillus lignieresii". The most prominent symptom is the swelling of the tongue that comes out of the mouth and is very hard at palpation ("wooden tongue").

"Actinobacillus suis" is an important disease of pigs of all ages and can lead to severe morbidity and sudden death.

Mouth actinobacillosis of cattle must be differentiated from actinomycosis that affects bone tissues of the maxilla.

Diagnosis is made with isolation of "Pasteurella multocida" in a normally sterile site (blood, pus, or cerebrospinal fluid).

Haemorrhagic septicaemia is one of the most economically important pasteurelloses. Haemorrhagic septicaemia in cattle and buffaloes was previously known to be associated with one of two serotypes of "P. multocida": Asian B:2 and African E:2 according to the Carter-Heddleston system, or 6:B and 6:E using the Namioka-Carter system.

The disease occurs mainly in cattle and buffaloes, but has also been reported in goats ("Capra aegagrus hircus"), African buffalo ("Syncerus nanus"), camels, horses and donkeys ("Equus africanus asinus"), in pigs infected by serogroup B, and in wild elephants ("Elephas maximus"). Serotypes B:1 and B:3,4 have caused a septicaemic disease in antelope ("Antilocapra americana") and elk ("Cervus canadensis"), respectively. Serotype B:4 was associated with the disease in bison ("Bison bison").

Serotypes E:2 and B:2 were associated with HS outbreaks in Africa and Asia respectively. Serotype E:2 was reported in Senegal, Mali, Guinea, Ivory Coast, Nigeria, Cameroon, the Central African Republic and Zambia. However, it is now inaccurate to associate outbreaks in Africa with serotype E:2 as many outbreaks of HS in Africa have now been associated with serogroup B. In the same manner, serogroup E has been associated with outbreaks in Asia. For instance, one record of "Asian serotype" (B:2) was reported in Cameroon. Some reports showed that serotype B:2 may be present in some East African countries. Both serogroups B and E have been reported in Egypt and Sudan.

Natural routes of infection are inhalation and/or ingestion. Experimental transmission has succeeded using intranasal aerosol spray or oral drenching. When subcutaneous inoculation is used experimentally, it results in rapid onset of the disease, a shorter clinical course and less marked pathological lesions compared to the longer course of disease and more profound lesions of oral drenching and the intranasal infection by aerosols.

When HS was introduced for the first time into a geographic area, morbidity and mortality rates were high, approaching 100% unless animals were treated in the very early stages of disease.

A wide variety of clinical signs have been described for HS in cattle and buffaloes. The incubation periods (the time between exposure and observable disease) for buffalo calves 4–10 months of age varies according to the route of infection. The incubation period is 12–14 hours, approximately 30 hours and 46–80 hours for subcutaneous infection, oral infection and natural exposure, respectively.

There is variability in the duration of the clinical course of the disease. In the case of experimental subcutaneous infection, the clinical course lasted only a few hours, while it persisted for 2–5 days following oral infection and in buffaloes and cattle that had been exposed to naturally-infected animals. It has also been recorded from field observations that the clinical courses of per-acute and acute cases were 4–12 hours and 2–3 days, respectively.

Generally, progression of the disease in buffaloes and cattle is divided into three phases. Phase one is characterised by fever, with a rectal temperature of , loss of appetite and depression. Phase two is typified by increased respiration rate (40–50/minute), laboured breathing, clear nasal discharge (turns opaque and mucopurulent as the disease progresses), salivation and submandibular oedema spreading to the pectoral (brisket) region and even to the forelegs. Finally, in phase three, there is typically recumbency, continued acute respiratory distress and terminal septicaemia. The three phases overlap when the disease course is short. In general, buffaloes have a more acute onset of disease than cattle, with a shorter duration.

Macrolides, tetracyclines and quinolones are active against "M. capricolum" subsp." capripneumoniae". Disease incidence is reduced by good hygiene and husbandry practices.

Movement restrictions and slaughtering infected animals are recommended for countries that are newly infected.

Pasteurellosis is an infection with a species of the bacterial genus "Pasteurella", which is found in humans and other animals.

"Pasteurella multocida" (subspecies "P. m. septica" and "P. m. multocida") is carried in the mouth and respiratory tract of various animals, including pigs. It is a small, Gram-negative bacillus with bipolar staining by Wayson stain. In animals, it can originate fulminant septicaemia (chicken cholera), but is also a common commensal.

Until taxonomic revision in 1999, "Mannheimia" spp. were classified as "Pasteurella" spp., and infections by organisms now called "Mannheimia" spp., as well as by organisms now called "Pasteurella" spp., were designated as pasteurellosis. The term "pasteurellosis" is often still applied to mannheimiosis, although such usage has declined.

Contagious caprine pleuropneumonia (CCPP) is a cause of major economic losses to goat producers in Africa, Asia and the Middle East.

Disease is caused by members of the Mycoplasma genus - usually "Mycoplasma capricolum subsp. capricolum" but sometimes by "M. mycoides" subsp. "capri" or "M. mycoides" subsp. "mycoides". It is extremely contagious with very high morbidity and mortality rates, causing an interstitial fibrinous pleuropneumonia in infected goats. Infection is spread by close-contact aerosol, therefore overcrowding and confinement increases disease incidence. Stress factors such as malnutrition and long transport can also predispose animals to disease.

Goats are the only species affected, therefore the disease is not a zoonosis. There is no age breed or sex predilection, but clinical signs are often worse in younger animals.

There has been anecdotal evidence provided by Elaine Ingham according to which susceptibility to facial eczema in cattle is related to nutrient deficiency of forage. The experiment, which Ingham conducted, showed that by improving soil biology the forage had better nutrient qualities and was associated with an elimination of the disease.

Phaeohyphomycosis is a heterogeneous group of mycotic infections caused by dematiaceous fungi whose morphologic characteristics in tissue include hyphae, yeast-like cells, or a combination of these. It can be associated an array of darkly-pigmented hyphomycetes including "Alternaria" species"," "Exophiala jeanselmei," and "Rhinocladiella mackenziei".

The term “phaeohyphomycosis” was introduced to determine infections caused by dematiaceous or pigmented filamentous fungi which contain melanin in their cell walls. Phaeohyphomycosis is an uncommon infection, however the number of case reported has been increasing in recent years. The presence of melanin in cell walls may be a virulence factor for the pathogens caused by the fungi. The outcome of antifungal treatment is poor, and mortality is almost 80%. Phaeohyphomycosis has been attributed to more than 100 species and 60 genera of fungi over the past several decades. The pathogens are considered opportunistic. Almost all cases of widely disseminated infection have occurred in immunosuppressed patients.

Extensive treatments have been used on domestic animals more than on wild animals, probably because infected domestic animals are easier to identify and treat than infected wildlife. Treatment plans and management vary across taxa because this disease tends to affect each species differently. Antifungal drugs are the first line of defense to kill the agents causing phaeohyphomycosis, but despite the significant progress made in the last two decades and a 30% increase in available antifungal drugs since 2000, many drugs are not effective against black fungi. Diseases caused black fungi are hard to treat because the fungi are very difficult to kill. This high resilience may be contributed to the presence of melanin in their cell walls. Current antifungal agents the fungi are not resistant to are posaconazole, voriconazole, and azole isavuconazole.

In 2006, a free-living Eastern box turtle, "Terrapene carolina carolina", was found with a form of phaeohyphomycosis and was brought in the Wildlife Center of Virginia. Its symptom was swelling of the right hindfoot; it was diagnosed as having chromomycosis by histopathology. The center provided a series of antimicrobial treatments and a one-month course of 1 mg itraconazole, administered orally once a day. The eastern box turtle was euthanized due to further complications and the caretakers’ belief that the turtle would not be able to survive if placed back in the wild.

A recent case of a form of phaeohyphomycosis infection was found in a dog in 2011. The Journal of the American Veterinary Medical Association published a case study in which researchers successfully managed an intracranial phaeohyphomycotic fungal granuloma in a one-year-old male Boxer dog. Veterinarians of the Department of Veterinary Clinical Sciences at Tufts University surgically removed the granuloma in the right cerebral hemisphere. The patient was treated with fluconazole for 4 months, and was followed with voriconazole for 10 months. Both are medications used to treat fungal infections. Based on magnetic resonance imaging and cerebrospinal fluid (CSF) analysis 8 months after the surgery, the male Boxer’s outcome was considered excellent.

Emphasis has been placed on how to manage this disease through careful management practices including: proper handling, preventing crowding situation with animals, and transportation. Both the animals and the environment should be treated thoroughly to hinder the spread and control the fungal infection. This is especially important since humans can also contract this disease.

In laboratory animals, prevention includes a low-stress environment, an adequate amount of nutritional feed, and appropriate sanitation measurements. Because animals likely ingest bacterial spores from contaminated bedding and feed, regular cleaning is a helpful method of prevention. No prevention methods are currently available for wild animal populations.

Green nails may be (1) due to a "Pseudomonas aeruginosa" infection causing a green nail syndrome or (2) the result of copper in tap water.

MAP is capable of causing Johne's-like symptoms in humans, though difficulty in testing for MAP infection presents a diagnostic hurdle.

Clinical similarities are seen between Johne's disease in ruminants and inflammatory bowel disease in humans, and because of this, some researchers contend the organism is a cause of Crohn's disease. However, epidemiologic studies have provided variable results; in certain studies, the organism (or an immune response directed against it) has been much more frequently found in patients with Crohn's disease than asymptomatic people.

Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many natural and artificial environments. It uses a wide range of organic material for food; in animals, the versatility enables the organism to infect damaged tissues or those with reduced immunity. The symptoms of such infections are generalized inflammation and sepsis. If such colonizations occur in critical body organs, such as the lungs, the urinary tract, and kidneys, the results can be fatal. Because it thrives on most surfaces, this bacterium is also found on and in medical equipment, including catheters, causing cross-infections in hospitals and clinics. It is implicated in hot-tub rash. It is also able to decompose hydrocarbons and has been used to break down tarballs and oil from oil spills.

In an endemic herd, only a minority of the animals develops clinical signs; most animals either eliminate the infection or become asymptomatic carriers. The mortality rate is about 1%, but up to 50% of the animals in the herd can be asymptomatically infected, resulting in losses in production. Once the symptoms appear, paratuberculosis is progressive and affected animals eventually die. The percentage of asymptomatic carriers that develop overt disease is unknown.

Facial eczema, FE, is a disease that mainly affects ruminants such as cattle, sheep, deer, goats and South American camelids (alpaca, llamas).

It is caused by the fungus "Pithomyces chartarum" that under favorable conditions can rapidly disseminate in pastures. The fungus requires warm humid weather with night time temperatures of over 13 °C (55 °F) for several days, and litter at the bottom of the sward.

"Pithomyces chartarum" occurs worldwide but is a problem predominantly where farm animals are intensively grazed, especially in New Zealand.

The spores of the fungus release the mycotoxin sporidesmin in the gastrointestinal tract, causing a blockage in the bile ducts that leads to injury of the liver. Bile, chlorophyll and other waste products consequently build up in the bloodstream causing photo sensitivity of the skin especially that exposed to direct sunlight. This in turn causes severe skin irritation that the animal attempts to relieve by rubbing its head against available objects, resulting in peeling of the skin.

The large family of fungi that produce mycotoxins, of which sporidesmin is one, live mainly on ryegrasses and can cause significant problems in grazing animals. Sporidesmin can lower an animals immunity and affect total production in farm animals, and, when taken in larger quantities, can result in death.

The clinical symptoms of FE are distressing: restlessness, frequent urination, shaking, persistent rubbing of the head against objects (e.g. fences, trees etc.), drooping and reddened ears, swollen eyes, and avoidance of sunlight by seeking shade. Exposed areas of skin develop weeping dermatitis and scabs that can become infected and attractive to blow-fly causing myiasis.

Over 400,000 cat bites are reported each year in the US, though the actual number of bites is much higher since many such bites are under-reported. 40 million households in the United States have domestic cats. Data on the number of people bitten or scratched by cats is limited because most of these incidents are not reported; however, 20%-80% of cat bites and scratches become infected. Cat-scratch disease or cat-scratch fever, an infection that causes fever and swollen lymph nodes, can develop from cat scratches even if they only break the surface of the skin. Based on reports of people treated for cat bites at hospitals, women are most likely to be victims of cat bites and scratches. Because of their smaller build, children are more likely to be bitten on their head, neck and face. Adults are more likely to bitten on the hands and arms. Those who are immunocompromised are more susceptible to infection from a cat bite.

Currently, antibiotic drugs such as penicillin or tetracycline are the only effective methods for disease treatment. Within wild populations, disease control consists of reducing the amount of bacterial spores present in the environment. This can be done by removing contaminated carcasses and scat.

Cat bites can often be prevented by:

- instructing children not to tease cats or other pets.

- being cautious with unfamiliar cats.

- approaching cats with care, even if they appear to be friendly.

- avoiding rough play with cats and kittens.

Rough play causes is perceived as aggressive. This will lead to the cat being defensive when approached by people. Preventing cat bites includes not provoking the cat.

Cutaneous actinomycosis is a chronic disease that affects the deep subcutaneous tissue of the skin. Caused by an anaerobic, Gram-positive, filamentous type of bacteria in the genus "Actinomyces", invasion of the soft tissue leads to the formation of abnormal channels leading to the skin surface (external sinus tracts) that discharge pale yellow sulfur granules.

This disease is uncommon, and has non-specific clinical features, making it difficult to diagnose.

Cervicofacial, pulmonary/thoracic and gastrointestinal forms exist, yet cervicofacial disease accounts for two-thirds of reported infections.