Clinical presentation of sparganosis most often occurs after the larvae have migrated to a subcutaneous location. The destination of the larvae is often a tissue or muscle in the chest, abdominal wall, extremities, or scrotum, although other sites include the eyes, brain, urinary tract, pleura, pericardium, and spinal canal. The early stages of disease in humans are often asymptomatic, but the spargana typically cause a painful inflammatory reaction in the tissues surrounding the subcutaneous site as they grow. Discrete subcutaneous nodules develop that may appear and disappear over a period of time. The nodules usually itch, swell, turn red, and migrate, and are often accompanied by painful edema. Seizures, hemiparesis, and headaches are also common symptoms of sparganosis, especially cerebral sparganosis, and eosinophilia is a common sign. Clinical symptoms also vary according to the location of the sparganum; possible symptoms include elephantiasis from location in the lymph channels, peritonitis from location in the intestinal perforation, and brain abscesses from location in the brain. In genital sparganosis, subcutaneous nodules are present in the groin, labia, or scrotum and may appear tumor-like.

Ocular sparganosis a particularly well-described type of sparganosis. Early signs of the ocular form include eye pain, epiphora (excessive watering of the eye), and/or ptosis (drooping of the upper eyelid). Other signs include periorbital edema and/or edematous swelling that resembles Romana’s sign in Chagas disease, lacrimation, orbital cellulitis, exophthalmos (protrusion of the eyeball), and/or an exposed cornea ulcer. The most common sign at presentation is a mass lesion in the eye. If untreated, ocular sparganosis can lead to blindness.

In one case of brain infestation by "Spirometra erinaceieuropaei", a man sought treatment on suffering headaches, seizures, memory flashbacks and strange smells. Magnetic resonance imaging (MRI) scans showed a cluster of rings, initially in the right medial temporal lobe, but moving over time to the other side of the brain. The cause was not determined for four years; ultimately a biopsy was performed and a 1 cm-long tapeworm was found and removed. The patient continued to suffer symptoms.

CNS symptoms begin with mild cognitive impairment and slowed reactions, and in a very severe form often progress to unconsciousness. Patients may present with neuropathic pain early in the infection. Eventually severe infection will lead to ascending weakness, quadriparesis, areflexia, respiratory failure, and muscle atrophy, and will lead to death if not treated. Occasionally patients present with cranial nerve palsies, usually in nerves 7 and 8, and rarely larvae will enter ocular structures. Even with treatment, damage to the CNS may be permanent and result in a variety of negative outcomes depending on the location of the infection, and the patient may suffer chronic pain as a result of infection.

Infection first presents with severe abdominal pain, nausea, vomiting, and weakness, which gradually lessens and progresses to fever, and then to CNS symptoms and severe headache and stiffness of the neck.

"Taenia saginata" infection is asymptomatic, but heavy infection causes weight loss, dizziness, abdominal pain, diarrhea, headaches, nausea, constipation, chronic indigestion, and loss of appetite. It can cause antigen reaction that induce allergic reaction. It is also a rare cause of ileus, pancreatitis, cholecystitis, and cholangitis.

There are accidental consumptions of eggs of "T. solium" from contaminated vegetables or water. The eggs enter the intestine where they develop into larvae. The larvae enter the bloodstream and invade host tissues. This clinical condition, called cysticercosis, is the most frequent and severe disease caused by any tapeworm. It can lead to severe headaches, dizziness, occasional seizures, dementia, hypertension, lesions in the brain, blindness, tumor-like growths, and low eosinophil levels. It is the cause of major neurological problems, such as hydrocephalus, paraplegy, meningitis, convulsions, and even death.

Light infestations (<100 worms) frequently have no symptoms. Heavier infestations, especially in small children, can present gastrointestinal problems including abdominal pain and distension, bloody or mucus-filled diarrhea, and tenesmus (feeling of incomplete defecation, generally accompanied by involuntary straining). Mechanical damage to the intestinal mucosa may occur, as well as toxic or inflammatory damage to the intestines of the host. While appendicitis may be brought on by damage and edema of the adjacent tissue, if there are large numbers of worms or larvae present, it has been suggested that the embedding of the worms into the ileocecal region may also make the host susceptible to bacterial infection. A severe infection with high numbers of embedded worms in the rectum leads to edema, which can cause rectal prolapse, although this is typically only seen in small children. The prolapsed, inflamed and edematous rectal tissue may even show visible worms.

Growth retardation, weight loss, nutritional deficiencies, and anemia (due to long-standing blood loss) are also characteristic of infection, and these symptoms are more prevalent and severe in children. It does not commonly cause eosinophilia.

Coinfection of "T. trichiura" with other parasites is common and with larger worm burdens can cause both exacerbation of dangerous trichuriasis symptoms such as massive gastrointestinal bleeding (shown to be especially dramatic with coinfection with "Salmonella typhi") and exacerbation of symptoms and pathogenesis of the other parasitic infection (as is typical with coinfection with "Schistosoma mansoni", in which higher worm burden and liver egg burden is common). Parasitic coinfection with HIV/AIDS, tuberculosis, and malaria is also common, especially in Sub-saharan Africa, and helminth coinfection adversely affects the natural history and progression of HIV/AIDS, tuberculosis, and malaria and can increase clinical malaria severity. In a study performed in Senegal, infections of soil-transmitted helminths like "T. trichiura" (as well as schistosome infections independently) showed enhanced risk and increased the incidence of malaria.

Heavy infestations may have bloody diarrhea. Long-standing blood loss may lead to iron-deficiency anemia. Vitamin A deficiency may also result due to infection.

Sparganosis is a parasitic infection caused by the plerocercoid larvae of the genus "Spirometra" including , "S. ranarum", "S. mansonoides" and "S. erinacei". It was first described by Patrick Manson from China in 1882, and the first human case was reported by Charles Wardell Stiles from Florida in 1908. The infection is transmitted by ingestion of contaminated water, ingestion of a second intermediate host such as a frog or snake, or contact between a second intermediate host and an open wound or mucous membrane. Humans are the accidental hosts in the life cycle, while dogs, cats, and other mammals are definitive hosts. Copepods (freshwater crustaceans) are the first intermediate hosts, and various amphibians and reptiles are second intermediate hosts.

Once a human becomes infected, the plerocercoid larvae migrate to a subcutaneous location, where they typically develop into a painful nodule. Migration to the brain results in cerebral sparganosis, while migration to the eyes results in ocular sparganosis. Sparganosis is most prevalent in Eastern Asia, although cases have been described in countries throughout the world. In total, approximately 300 cases have been described in the literature up to 2003. Diagnosis is typically not made until the sparganum larva has been surgically removed. Praziquantel is the drug of choice, although its efficacy is unknown and surgical removal of the sparganum is generally the best treatment. Public health interventions should focus on water and dietary sanitation, as well as education about the disease in rural areas and discouragement of the use of poultices.

Adult flukes are known to be quite harmless, as they do not attack on the host tissue. It is the immature flukes which are most damaging as they get attached to the intestinal wall, literally and actively sloughing off of the tissue. This necrosis is indicated by haemorrhage in faeces, which in turn is a sign of severe enteritis. Under such condition the animals become anorexic and lethargic. It is often accompanied by pronounced diarrhoea, dehydration, oedema, polydipsia, anaemia, listlessness and weight loss. In sheep profuse diarrhoea usually develops two to four weeks after initial infection. If infection is not properly attended death can ensue within 20 days, and in a farm mortality can be very high. In fact there are intermittent reports of mortality as high as 80% among sheep and cattle. Sometimes chronic form is also seen with severe emaciation, anaemia, rough coat, mucosal oedema, thickened duodenum and oedema in the sub maxillary space. The terminally sick animals lie prostrate on the ground, completely emaciated until they die. In buffalos, severe haemorrhage was found to be associated with liver cirrhosis and nodular hepatitis.

Trichuriasis, also known as whipworm infection, is an infection by the parasitic worm "Trichuris trichiura" (whipworm). If infection is only with a few worms, there are often no symptoms. In those who are infected with many worms, there may be abdominal pain, tiredness and diarrhea. The diarrhea sometimes contains blood. Infections in children may cause poor intellectual and physical development. Low red blood cell levels may occur due to loss of blood.

The disease is usually spread when people eat food or drink water that contains the eggs of these worms. This may occur when contaminated vegetables are not fully cleaned or cooked. Often these eggs are in the soil in areas where people defecate outside and where untreated human feces is used as fertilizer. These eggs originate from the feces of infected people. Young children playing in such soil and putting their hands in their mouths also become infected easily. The worms live in the large bowel and are about four centimetres in length. Whipworm is diagnosed by seeing the eggs when examining the stool with a microscope. Eggs are barrel-shaped. Trichuriasis belongs to the group of soil-transmitted helminthiases.

Prevention is by properly cooking food and hand washing before cooking. Other measures include improving access to sanitation such as ensuring use of functional and clean toilets and access to clean water. In areas of the world where the infections are common, often entire groups of people will be treated all at once and on a regular basis. Treatment is with three days of the medication: albendazole, mebendazole or ivermectin. People often become infected again after treatment.

Whipworm infection affected about 464 million in 2015. It is most common in tropical countries. In the developing world, those infected with whipworm often also have hookworms and ascariasis infections. They have a large effect on the economy of many countries. Work is ongoing to develop a vaccine against the disease. Trichuriasis is classified as a neglected tropical disease.

There are no specific symptoms or signs of hookworm infection, but they give rise to a combination of intestinal inflammation and progressive iron-deficiency anemia and protein deficiency. Coughing, chest pain, wheezing, and fever will sometimes result from severe infection. Epigastric pains, indigestion, nausea, vomiting, constipation, and diarrhea can occur early or in later stages as well, although gastrointestinal symptoms tend to improve with time. Signs of advanced severe infection are those of anemia and protein deficiency, including emaciation, cardiac failure and abdominal distension with ascites.

Larval invasion of the skin (mostly in the Americas) can produce a skin disease called cutaneous larva migrans also known as "creeping eruption". The hosts of these worms are not human and the larvae can only penetrate the upper five layers of the skin, where they give rise to intense, local itching, usually on the foot or lower leg, known as "ground itch". This infection is due to larvae from the "A. Braziliense" hookworm. The larvae migrate in tortuous tunnels between the "stratum basale" and "stratum corneum" of the skin, causing serpiginous vesicular lesions. With advancing movement of the larvae, the rear portions of the lesions become dry and crusty. The lesions are typically intensely itchy.

The term "hookworm" is sometimes used to refer to hookworm infection. A hookworm is a type of parasitic worm (helminth).

Strongyloides infection occurs in five forms. On acquiring the infection, there may be respiratory symptoms (Löffler's syndrome). The infection may then become chronic with mainly digestive symptoms. On reinfection (when larvae migrate through the body), there may be respiratory, skin and digestive symptoms. Finally, the hyperinfection syndrome causes symptoms in many organ systems, including the central nervous system.

Frequently asymptomatic. Gastrointestinal system symptoms include abdominal pain and diarrhea. Pulmonary symptoms (including Löffler's syndrome) can occur during pulmonary migration of the filariform larvae. Dermatologic manifestations include urticarial rashes in the buttocks and waist areas as well as larva currens. Eosinophilia is generally present.

Strongyloidiasis can become chronic and then become completely asymptomatic.

Amphistomiasis or paramphistomiasis (alternatively spelled amphistomosis or paramphistomosis) is a parasitic disease of livestock animals, more commonly of cattle and sheep, and humans caused by immature helminthic flatworms belonging to the order Echinostomida. The term amphistomiasis is used for broader connotation implying the disease inflicted by members of Echinostomida including the family Paramphistomidae/Gastrodiscidae (to be precise, the species "Gastrodiscoides hominis"); whereas paramphistomiasis is restricted to that of the members of the family Paramphistomatidae only. "G. discoides" and "Watsonius watsoni" are responsible for the disease in humans, while most paramphistomes are responsible in livestock animals, and some wild mammals. In livestock industry the disease causes heavy economic backlashes due to poor production of milk, meat and wool.

Dientamoebiasis is a medical condition caused by infection with "Dientamoeba fragilis", a single-cell parasite that infects the lower gastrointestinal tract of humans. It is an important cause of traveler's diarrhea, chronic abdominal pain, chronic fatigue, and failure to thrive in children.

The most commonly reported symptoms in conjunction with infection with "D. fragilis" include abdominal pain (69%) and diarrhea (61%). Diarrhea may be intermittent and may not be present in all cases. It is often chronic, lasting over two weeks. The degree of symptoms may vary from asymptomatic to severe, and can include weight loss, vomiting, fever, and involvement of other digestive organs.

Symptoms may be more severe in children. Additional symptoms reported have included:

1. Weight loss

2. Fatigue

3. Nausea and vomiting

4. Fever

5. Urticaria (skin rash)

6. Pruritus (itchiness)

7. Biliary infection

Researchers have published conflicting reports concerning whether "Blastocystis" causes symptoms in humans, with one of the earliest reports in 1916. The incidence of reports associated with symptoms began to increase in 1984, with physicians from Saudi Arabia reporting symptoms in humans and US physicians reporting symptoms in individuals with travel to less developed countries. A lively debate ensued in the early 1990s, with some physicians objecting to publication of reports that "Blastocystis" caused disease. Some researchers believe the debate has been resolved by finding of multiple species of "Blastocystis" that can infect humans, with some causing symptoms and others being harmless (see Genetics and Symptoms).

A few of most commonly reported symptoms are:

- abdominal pain

- itching, usually anal itching

- constipation

- diarrhea

- watery or loose stools

- weight loss

- fatigue

- flatulence

Some less commonly reported symptoms include:

- Skin rash

- Headache, depression

- Arthritic symptoms and joint pain

- Intestinal inflammation

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.

Blastocystosis refers to a medical condition caused by infection with "Blastocystis". "Blastocystis" is a protozoal, single-celled parasite that inhabits the gastrointestinal tracts of humans and other animals. Many different types of "Blastocystis" exist, and they can infect humans, farm animals, birds, rodents, amphibians, reptiles, fish, and even cockroaches. Blastocystosis has been found to be a possible risk factor for development of IBS (Irritable Bowel Syndrome).

Cats are reservoirs and are able to transmit mycotic infections. Cats, especially kittens can pass on a Ringworm infection to people. Ringworm is a fungal disease and approximately 40 types of fungi can cause ringworm. They are typically of the "Trichophyton", "Microsporum", or "Epidermophyton" type. It gets its name from the characteristic ring-like rash on the skin. The disease is spread by touching an infected cat. The rash may be scaly, reddened, and circular. Ringworm on the scalp usually makes a bald patch of scaly skin. Long-haired cats do not always show signs of ringworm infection. Kittens with ringworm have patches that are hairless, circular, or irregularly shaped areas of scaling, crusting, and redness that may or may not be itchy. The area may not be completely hairless, and instead have brittle, broken hairs. If the claws are affected, they may have a whitish, opaque appearance with shredding of the claw's surface.

Sporotrichosis is a fungal disease that is transmitted by mostly outdoor cats.

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.

Most infected cats have been healthy before a very sudden onset of severe disease. The course of clinical disease is often swift with clinical signs of lethargy and inappetence within 5 to 20 days after the tick bite. Cats develop a high fever, but the temperature may become low before death. Other clinical findings can be: dehydration, icterus (jaundice), enlarged liver and spleen, lymphadenopathy, pale mucus membranes, respiratory distress, tachycardia or bradycardia, and tick infestation (although ticks are not often found on infected cats since cats typically groom ticks off their fur). Signs of disease seen on blood work include hemolytic anemia, thrombocytopenia, increased or decreased white blood cell numbers, icterus, and elevated liver enzymes. Death usually follows the onset of clinical signs within a few days. However, more recent studies show not all cats develop clinical signs after infection, and some cats survive the infection.

Acute toxoplasmosis is often asymptomatic in healthy adults. However, symptoms may manifest and are often influenza-like: swollen lymph nodes, headaches, fever, and fatigue, or muscle aches and pains that last for a month or more. Rarely will a human with a fully functioning immune system develop severe symptoms following infection. People with weakened immune systems are likely to experience headache, confusion, poor coordination, seizures, lung problems that may resemble tuberculosis or Pneumocystis jiroveci pneumonia (a common opportunistic infection that occurs in people with AIDS), or blurred vision caused by severe inflammation of the retina (ocular toxoplasmosis) Young children and immunocompromised people, such as those with HIV/AIDS, those taking certain types of chemotherapy, or those who have recently received an organ transplant, may develop severe toxoplasmosis. This can cause damage to the brain (encephalitis) or the eyes (necrotizing retinochoroiditis). Infants infected via placental transmission may be born with either of these problems, or with nasal malformations, although these complications are rare in newborns. The toxoplasmic trophozoites causing acute toxoplasmosis are referred to as tachyzoites, and are typically found in bodily fluids.

Swollen lymph nodes are commonly found in the neck or under the chin, followed by the armpits and the groin. Swelling may occur at different times after the initial infection, persist, and recur for various times independently of antiparasitic treatment. It is usually found at single sites in adults, but in children, multiple sites may be more common. Enlarged lymph nodes will resolve within one to two months in 60% of cases. However, a quarter of those affected take two to four months to return to normal, and 8% take four to six months. A substantial number (6%) do not return to normal until much later.

Due to its asymptomatic nature, it is easy for a host to become infected with "Toxoplasma gondii" and develop toxoplasmosis without knowing it. Although mild, flu-like symptoms occasionally occur during the first few weeks following exposure, infection with "T. gondii" produces no readily observable symptoms in healthy human adults. In most immunocompetent people, the infection enters a latent phase, during which only bradyzoites (tissue cysts) are present; these tissue cysts and even lesions can occur in the retinas, alveolar lining of the lungs (where an acute infection may mimic a "Pneumocystis jirovecii" infection), heart, skeletal muscle, and the central nervous system (CNS), including the brain. Cysts form in the CNS (brain tissue) upon infection with "T. gondii" and persist for the lifetime of the host. Most infants who are infected while in the womb have no symptoms at birth, but may develop symptoms later in life.

Reviews of serological studies have estimated that 30–50% of the global population has been exposed to and may be chronically infected with latent toxoplasmosis, although infection rates differ significantly from country to country. This latent state of infection has recently been associated with numerous disease burdens, neural alterations, and subtle gender-dependent behavioral changes in immunocompetent humans.

Murine typhus (also called endemic typhus) is a form of typhus transmitted by fleas (Xenopsylla cheopis), usually on rats. (This is in contrast to epidemic typhus, which is usually transmitted by lice.) Murine typhus is an under-recognized entity, as it is often confused with viral illnesses. Most people who are infected do not realize that they have been bitten by fleas.