Recommendations for the diagnosis of congenital toxoplasmosis include: prenatal diagnosis based on testing of amniotic fluid and ultrasound examinations; neonatal diagnosis based on molecular testing of placenta and cord blood and comparative mother-child serologic tests and a clinical examination at birth; and early childhood diagnosis based on neurologic and ophthalmologic examinations and a serologic survey during the first year of life. During pregnancy, serological testing is recommended at three week intervals.

Even though diagnosis of toxoplasmosis heavily relies on serological detection of specific anti-"Toxoplasma" immunoglobulin, serological testing has limitations. For example, it may fail to detect the active phase of "T. gondii" infection because the specific anti-"Toxoplasma" IgG or IgM may not be produced until after several weeks of infection. As a result, a pregnant woman might test negative during the active phase of "T. gondii" infection leading to undetected and therefore untreated congenital toxoplasmosis. Also, the test may not detect "T. gondii" infections in immunocompromised patients because the titers of specific anti-"Toxoplasma" IgG or IgM may not rise in this type of patient.

Many PCR-based techniques have been developed to diagnose toxoplasmosis using clinical specimens that include amniotic fluid, blood, cerebrospinal fluid, and tissue biopsy. The most sensitive PCR-based technique is nested PCR, followed by hybridization of PCR products. The major downside to these techniques is that they are time consuming and do not provide quantitative data.

Real-time PCR is useful in pathogen detection, gene expression and regulation, and allelic discrimination. This PCR technique utilizes the 5' nuclease activity of "Taq" DNA polymerase to cleave a nonextendible, fluorescence-labeled hybridization probe during the extension phase of PCR. A second fluorescent dye, e.g., 6-carboxy-tetramethyl-rhodamine, quenches the fluorescence of the intact probe. The nuclease cleavage of the hybridization probe during the PCR releases the effect of quenching resulting in an increase of fluorescence proportional to the amount of PCR product, which can be monitored by a sequence detector.

Toxoplasmosis cannot be detected with immunostaining. Lymph nodes affected by "Toxoplasma" have characteristic changes, including poorly demarcated reactive germinal centers, clusters of monocytoid B cells, and scattered epithelioid histiocytes.

The classic triad of congenital toxoplasmosis includes: chorioretinitis, hydrocephalus, and intracranial artheriosclerosis.

Diagnosis of toxoplasmosis in humans is made by biological, serological, histological, or molecular methods, or by some combination of the above. Toxoplasmosis can be difficult to distinguish from primary central nervous system lymphoma. It mimics several other infectious diseases so clinical signs are non-specific and are not sufficiently characteristic for a definite diagnosis. As a result, the diagnosis is made by a trial of therapy (pyrimethamine, sulfadiazine, and folinic acid (USAN: leucovorin)), if the drugs produce no effect clinically and no improvement on repeat imaging.

"T. gondii" may also be detected in blood, amniotic fluid, or cerebrospinal fluid by using polymerase chain reaction. "T. gondii" may exist in a host as an inactive cyst that would likely evade detection.

Serological testing can detect "T. gondii" antibodies in blood serum, using methods including the Sabin–Feldman dye test (DT), the indirect hemagglutination assay, the indirect fluorescent antibody assay (IFA), the direct agglutination test, the latex agglutination test (LAT), the enzyme-linked immunosorbent assay (ELISA), and the immunosorbent agglutination assay test (IAAT).

The most commonly used tests to measure IgG antibody are the DT, the ELISA, the IFA, and the modified direct agglutination test. IgG antibodies usually appear within a week or two of infection, peak within one to two months, then decline at various rates. "Toxoplasma" IgG antibodies generally persist for life, and therefore may be present in the bloodstream as a result of either current or previous infection.

To some extent, acute toxoplasmosis infections can be differentiated from chronic infections using an IgG avidity test, which is a variation on the ELISA. In the first response to infection, toxoplasma-specific IgG has a low affinity for the toxoplasma antigen; in the following weeks and month, IgG affinity for the antigen increases. Based on the IgG avidity test, if the IgG in the infected individual has a high affinity, it means that the infection began three to five months before testing. This is particularly useful in congenital infection, where pregnancy status and gestational age at time of infection determines treatment.

In contrast to IgG, IgM antibodies can be used to detect acute infection, but generally not chronic infection. The IgM antibodies appear sooner after infection than the IgG antibodies and disappear faster than IgG antibodies after recovery. In most cases, "T. gondii"-specific IgM antibodies can first be detected approximately a week after acquiring primary infection, and decrease within one to six months; 25% of those infected are negative for "T. gondii"-specific IgM within seven months. However, IgM may be detectable months or years after infection, during the chronic phase, and false positives for acute infection are possible. The most commonly used tests for the measurement of IgM antibody are double-sandwich IgM-ELISA, the IFA test, and the immunosorbent agglutination assay (IgM-ISAGA). Commercial test kits often have low specificity, and the reported results are frequently misinterpreted.

One way to diagnose "C. felis" is by taking blood and performing a peripheral blood smear to look for the erythrocytic piroplasms. The erythrocytic piroplasms are usually shaped like signet rings and are 1 to 1.5 µm. Not all cats that are infected will have the piroplasms on their blood smear, especially if they are early in disease course. Another method of diagnosing infection in sick cats is to take needle aspirates of affected organs and find the schizonts inside mononuclear cells in the tissues; examination of tissue is also useful for the diagnosis after cats have died. Blood samples can be sent away for polymerase chain reaction (PCR) testing to confirm infection. Other diseases that might resemble cytauxzoonosis should be ruled out. A major rule-out for "C. felis" is "Mycoplasma haemofelis" (formerly known as "Haemobartonella felis"); clinical signs can be similar to cytauxzoonosis and the organism may be confused on the peripheral smear. Because it causes similar signs in outdoor cats during the spring and summer, tularemia is another disease the veterinarian may want to rule out.

Other laboratory tests are often abnormal in sick cats. The CBC of an infected cat often shows a pancytopenia, or a decrease in red blood cells, white blood cells, and platelets; in some cases there is not a decrease in all three values. Clotting tests may be prolonged. Increased liver enzymes are common, and electrolyte disturbances, hyperglycemia, and acid-base disturbances can also be observed.

Dependent on the infectious syndrome, symptoms include fever, fatigue, dry cough, headache, blurred vision, and confusion. Symptom onset is often subacute, progressively worsened over several weeks. The two most common presentations are meningitis (an infection in and around the brain) and pulmonary (lung) infection.

Detection of cryptococcal antigen (capsular material) by culture of CSF, sputum and urine provides definitive diagnosis. Blood cultures may be positive in heavy infections. India ink of the CSF is a traditional microscopic method of diagnosis, although the sensitivity is poor in early infection, and may miss 15-20% of patients with culture-positive cryptococcal meningitis. Unusual morphological forms are rarely seen. Cryptococcal antigen from cerebrospinal fluid is the best test for diagnosis of cryptococcal meningitis in terms of sensitivity. Apart from conventional methods of detection like direct microscopy and culture, rapid diagnostic methods to detect cryptococcal antigen by latex agglutination test, lateral flow immunochromatographic assay (LFA), or enzyme immunoassay (EIA). A new cryptococcal antigen LFA was FDA approved in July 2011. Polymerase chain reaction (PCR) has been used on tissue specimens.

Cryptococcosis can rarely occur in the non-immunosuppressed people, particularly with "Cryptococcus gattii".

"Bartonella" growth rates improve when cultured in an enrichment inoculation step in a liquid insect-based medium such as "Bartonella" α-Proteobacteria Growth Medium (BAPGM) or Schneider’s Drosophila-based insect powder medium. Several studies have optimized the growing conditions of "Bartonella" spp. cultures in these liquid media, with no change in bacterial protein expressions or host interactions "in vitro". Insect-based liquid media supports the growth and co-culturing of at least seven "Bartonella" species, reduces bacterial culturing time and facilitates PCR detection and isolation of "Bartonella" spp. from animal and patient samples. Research shows that DNA may be detected following direct extraction from blood samples and become negative following enrichment culture, thus PCR is recommended after direct sample extraction and also following incubation in enrichment culture. Several studies have successfully optimized sensitivity and specificity by using PCR amplification (pre-enrichment PCR) and enrichment culturing of blood draw samples, followed by PCR (post-enrichment PCR) and DNA sequence identification.

Cryptococcosis is a very subacute infection with a prolonged subclinical phase lasting weeks to months in persons with HIV/AIDS before the onset of symptomatic meningitis. In Sub-Saharan Africa, the prevalence rates of detectable cryptococcal antigen in peripheral blood is often 4–12% in persons with CD4 counts lower than 100 cells/mcL.

Cryptococcal antigen screen and preemptive treatment with fluconazole is cost saving to the healthcare system by avoiding cryptococcal meningitis. The World Health Organization recommends cryptococcal antigen screening in HIV-infected persons entering care with CD4<100 cells/μL. This undetected subclinical cryptococcal (if not preemptively treated with anti-fungal therapy) will often go on to develop cryptococcal meningitis, despite receiving HIV therapy. Cryptococcosis accounts for 20-25% of the mortality after initiating HIV therapy in Africa. What is effective preemptive treatment is unknown, with the current recommendations on dose and duration based on expert opinion. Screening in the United States is controversial, with official guidelines not recommending screening, despite cost-effectiveness and a 3% U.S. cryptococcal antigen prevalence in CD4<100 cells/μL.

The CDC states that PCR testing from a single blood draw is not sufficiently sensitive for "B." "henselae" testing, and can result in high false negative rates due to a small sample volume and levels below the limit of molecular detection.

"Bartonella" spp. are fastidious, slow-growing bacteria that are difficult to grow using traditional solid agar plate culture methods due to complex nutritional requirements and potentially a low number of circulating bacteria. This conventional method of culturing "Bartonella" spp. from blood inoculates plated directly onto solid agar plates requires an extended incubation period of 21 days due to the slow growth rate.

If an animal is suspected of lungworm infection, there are many ways to detect this parasitic infection such as performing one or more of the following techniques: a complete medical history including lung auscultation (stethoscope examination), doing a chest xray, fecal examination for detection of ova or larvae, examination of respiratory secretions for ova or larvae, and/or a complete blood count (CBC) to check for signs of increase in eosinophils

One strategy for the prevention of infection transmission between cats and people is to better educate people on the behaviour that puts them at risk for becoming infected.

Those at the highest risk of contracting a disease from a cat are those with behaviors that include: being licked, sharing food, sharing kithchen utensils, kissing, and sleeping with a cat. The very young, the elderly and those who are immunocompromised increase their risk of becoming infected when sleeping with their cats (and dogs). The CDC recommends that cat owners not allow a cat to lick your face because it can result in disease transmission. If someone is licked on their face, mucous membranes or an open wound, the risk for infection is reduced if the area is immediately washed with soap and water. Maintaining the health of the animal by regular inspection for fleas and ticks, scheduling deworming medications along with veterinary exams will also reduce the risk of acquiring a feline zoonosis.

Recommendations for the prevention of ringworm transmission to people include:

- regularly vacuuming areas of the home that pets commonly visit helps to remove fur or flakes of skin

- washing the hands with soap and running water after playing with or petting your pet.

- wearing gloves and long sleeves when handling cats infected with.

- disinfect areas the pet has spent time in, including surfaces and bedding.

- the spores of this fungus can be killed with common disinfectants like chlorine bleach diluted 1:10 (1/4 cup in 1 gallon of water), benzalkonium chloride, or strong detergents.

- not handling cats with ringworm by those whose immune system is weak in any way (if you have HIV/AIDS, are undergoing cancer treatment, or are taking medications that suppress the immune system, for example).

- taking the cat to the veterinarian if ringworm infection is suspected.

Diagnosis of effusive FIP has become more straightforward in recent years: detection of viral RNA in a sample of the effusion, by reverse-transcriptase polymerase chain reaction (RT-PCR) is diagnostic of effusive FIP. However, that does require that a sample be sent to an external veterinary laboratory. Within the veterinary hospital there are a number of tests which can rule out a diagnosis of effusive FIP within minutes:

1. Measure the total protein in the effusion: if it is less than 35g/l, FIP is extremely unlikely.

2. Measure the albumin to globulin ratio in the effusion: if it is over 0.8, FIP is ruled out, if it is less than 0.4, FIP is a possible—but not certain—diagnosis

3. Examine the cells in the effusion: if they are predominantly lymphocytes then FIP is excluded as a diagnosis.

Because FIP is an immune-mediated disease, treatment falls into two categories: direct action against the virus itself and modulation of the immune response.

In most instances, the diagnosis of toxoplasmic retinochoroiditis is made clinically on the basis of the appearance of the characteristic lesion on eye examination.

Seropositivity (positive blood test result) for Toxoplasma is very common and therefore not useful in diagnosis; however, a negative result i.e. absence of antibodies is often used to rule out disease. Others believe that serology is useful to confirm active toxoplasmic retinochoroiditis, not only by showing positivity but by also showing a significant elevation of titers: The mean IgG values were 147.7 ± 25.9 IU/ml for patients with active disease versus 18.3 ± 20.8 IU/ml for normal individuals.

Antibodies against Toxoplasma:

- IgG : appear within the first 2 weeks after infection, typically remain detectable for life, albeit at low levels;and may cross the placenta.

- IgM : rise early during the acute phase of the infection, typically remain detectable for less than 1 year, and do not cross the placenta.

- IgA : Measurement of IgA antibody titers may also be useful in a diagnosis of congenital toxoplasmosis in a fetus or newborn because IgM production is often weak during this period and the presence of IgG antibodies may indicate passive transfer of maternal antibodies in utero. IgA antibodies however usually disappear by 7 months.

In atypical cases, ocular fluid testing to detect parasite DNA by polymerase chain reaction or to determine intraocular production of specific antibody may be helpful for establishing etiology.

Neuroimaging is warranted in AIDS patients presenting with these findings because intracranial toxoplasmic lesions have been reported in up to 29% of these patients who have toxoplasmic chorioretinitis.

The preventative measure of keeping cats inside in areas with high infection rates can prevent infection. Approved tick treatments for cats can be used but have been shown not to fully prevent tick bites.

The most often used treatments for cytauxzoonosis are imidocarb dipropionate and a combination of atovaquone and azithromycin. Although imidocarb has been used for years, it is not particularly effective. In a large study, only 25% of cats treated with this drug and supportive care survived. 60% of sick cats treated with supportive care and the combination of the anti-malarial drug atovaquone and the antibiotic azithromycin survived infection.

Quick referral to a veterinarian equipped to treat the disease may be beneficial. All infected cats require supportive care, including careful fluids, nutritional support, treatment for complications, and often blood transfusion.

Cats that survive the infection should be kept indoors as they can be persistent carriers after surviving infection and might indirectly infect other cats after being themselves bitten by a vector tick.

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.

The diagnosis is aided by obtaining a history of the circumstances surrounding the bite. The time the bite was experienced, the location of the bite, and examination of the bite is noted. The person may have drainage from the site of the bite. They may also be febrile. Swelling may also occur. Because the wound from the bite may have healed over the punctures, the wound it may be opened and explored. The site is anesthetized prior to exploration of the wound for is examined for damage. Neurovascular status is assessed. Immune status may determine treatment as does

the presence of transplanted tissue or organs, rheumatic disease, diabetes, HIV/AIDS and sickle cell disease.

Swollen glands (lymph nodes) and red streaks radiating upward may be evident.

The diagnosis of a cat with rabies is evident by observing the cat. Cats with rabies may also appear restless, pant, and attack other animals, people, or objects. Animals with rabies typically die within a few days of appearing sick. Vaccination of the cat can prevent rabies being transmitted by the cat through a bite. If the cat is suspected of being infected with rabies, the person begins treatment with rabies vaccine.

Finding "Toxocara" larvae within a patient is the only definitive diagnosis for toxocariasis; however, biopsies to look for second stage larvae in humans are generally not very effective. PCR, ELISA, and serological testing are more commonly used to diagnose "Toxocara" infection. Serological tests are dependent on the number of larvae within the patient, and are unfortunately not very specific. ELISAs are much more reliable and currently have a 78% sensitivity and a 90% specificity. A 2007 study announced an ELISA specific to "Toxocara canis", which will minimize false positives from cross reactions with similar roundworms and will help distinguish if a patient is infected with "T. canis" or "T. cati". OLM is often diagnosed after a clinical examination. Granulomas can be found throughout the body and can be visualized using ultrasound, MRI, and CT technologies.

Repeat chest X-rays in 2 and 4 weeks after treatment. Also, recheck a fecal sample to monitor for the presence of larvae or ova in 2 to 4 weeks. This will confirm if the parasite is still living inside the respiratory tissue.

Some disease-carrying arthropods use cats as a vector, or carrier. Fleas and ticks can carry pathogenic organisms that infect a person with Lyme disease, tick borne encephalitis, and Rocky mountain spotted fever

Cat-scratch disease is characterized by granulomatous inflammation on histological examination of the lymph nodes. Under the microscope, the skin lesion demonstrates a circumscribed focus of necrosis, surround by histiocytes, often accompanied by multinucleated giant cells, lymphocytes, and eosinophils. The regional lymph nodes demonstrate follicular hyperplasia with central stellate necrosis with neutrophils, surrounded by palisading histiocytes (suppurative granulomas) and sinuses packed with monocytoid B cells, usually without perifollicular and intrafollicular epithelioid cells. This pattern, although typical, is only present in a minority of cases.

The Warthin–Starry stain can be helpful to show the presence of "B. henselae", but is often difficult to interpret. "B. henselae" is difficult to culture and can take 2–6 weeks to incubate. The best diagnostic method currently available is polymerase chain reaction, which has a sensitivity of 43-76% and a specificity (in one study) of 100%.

Diagnosis of FVR is usually by clinical signs, especially corneal ulceration. Definitive diagnosis can be done by direct immunofluorescence or virus isolation. However, many healthy cats are subclinical carriers of feline herpes virus, so a positive test for FHV-1 does not necessarily indicate that signs of an upper respiratory tract infection are due to FVR. Early in the course of the disease, histological analysis of cells from the tonsils, nasal tissue, or nictitating membrane (third eyelid) may show inclusion bodies (a collection of viral particles) within the nucleus of infected cells.

Ear mites of dogs and cats can be treated with any of the spot-on preparations available from veterinary surgeons as well as over the counter at many pet stores and online. If the chosen solution does not destroy mite eggs, treatment should be repeated after one month, to catch the next generation of mites that will have hatched by then. Relief, in terms of the cat or dog no longer scratching at his or her ears, will be noticeable within a few hours. However, since mite irritation is partly allergic (see scabies), symptoms may also outlive mites by weeks. Moreover, it may take topical antibiotics and several weeks to clear infected external wounds caused by scratching on the exterior surfaces of cat and dog ears.

Common home remedy treatment options include household ingredients such as isopropyl alcohol, acetic acid (vinegar), boric acid, tea tree oil, coconut oil, and many other plant based extracts, in varying proportions.

Option for treating ear mites in rabbits are the related antiparasitics ivermectin and selamectin. Both of these antiparasitics have also been used with good effect in cats and dogs. A topical preparation of 0.01% ivermectin (Acarexx) can be used directly as an oil in cat ears, and the related new generation drug selamectin (brand name "Revolution") is available as a once-per-month skin treatment for both dogs and cats, which will prevent new mite infestation as well as a number of other parasitic diseases. As with ivermectin, selamectin must be used with caution in collies and herder breeds with the possibility for homozygous MDR1 mutations. A single treatment with a topical formulation containing fipronil, (S)-methoprene, eprinomectin and praziquantel was shown to be efficient for the prevention of "Otodectes cynotis" infestation in cats.

"Toxoplasma" infection can be prevented in large part by:

- cooking meat to a safe temperature (i.e., one sufficient to kill "Toxoplasma")

- peeling or thoroughly washing fruits and vegetables before eating

- cleaning cooking surfaces and utensils after they have contacted raw meat, poultry, seafood, or unwashed fruits or vegetables

- pregnant women avoiding changing cat litter or, if no one else is available to change the cat litter, using gloves, then washing hands thoroughly

- not feeding raw or undercooked meat to cats to prevent acquisition of "Toxoplasma"

Prolonged and intense rainfall periods are significantly associated with the reactivation of toxoplasmic retinochoroiditis. Changes promoted by this climatic condition concern both the parasite survival in the soil as well as a putative effect on the host immune response due to other comorbidities.

There is a vaccine for FHV-1 available (ATCvet code: , plus various combination vaccines), but although it limits or weakens the severity of the disease and may reduce viral shedding, it does not prevent infection with FVR. Studies have shown a duration of immunity of this vaccine to be at least three years. The use of serology to demonstrate circulating antibodies to FHV-1 has been shown to have a positive predictive value for indicating protection from this disease.

Actively involving veterinarians and pet owners is important for controlling the transmission of "Toxocara" from pets to humans. A group very actively involved in promoting a reduction of infections in dogs in the United States is the Companion Animal Parasite Council -- CAPC. Since pregnant or lactating dogs and cats and their offspring have the highest, active parasitic load, these animals should be placed on a deworming program. Pet feces should be picked up and disposed of or buried, as they may contain "Toxocara" eggs. Practicing this measure in public areas, such as parks and beaches, is especially essential for decreasing transmission. Up to 20% of soil samples of U.S. playgrounds have found roundworm eggs. Also, sandboxes should be covered when not in use to prevent cats from using them as litter boxes. Hand washing before eating and after playing with pets, as well as after handling dirt will reduce the chances of ingesting "Toxocara" eggs. Washing all fruits and vegetables, keeping pets out of gardens and thoroughly cooking meats can also prevent transmission. Finally, teaching children not to place nonfood items, especially dirt, in their mouths will drastically reduce the chances of infection.

Toxocariasis has been named one of the neglected diseases of U.S. poverty, because of its prevalence in Appalachia, the southern U.S., inner city settings, and minority populations. Unfortunately, there is currently no vaccine available or under development. However, the mitochondrial genomes of both "T. cati" and "T. canis" have recently been sequenced, which could lead to breakthroughs in treatment and prevention.