Parasitology - Chapter 16, Parasites of Public Health Importance in Veterinary Parasitology

This affects humans, particularly pregnant women, her developing fetus, and individuals with AIDS. The domestic cat is the ONLY definitive host. The symptoms for the congenital form of this infection are abortion, infected CNS which causes neurological abnormalities, stillbirth, or a child with intellectual disabilities. The symptoms of the acquired form of this infection are lymphadenopathy, malaise, fever, lymphocytosis, and myocarditis

Toxoplasmosis

This form of Toxoplasmosis occurs when a woman becomes infected during pregnancy by ingesting sporulated oocysts (from the feces of the cat), and the tachyzoites (rapidly multiplying stages) can infect the developing fetus

Congenital

This form of Toxoplasmosis occurs when the human ingests the sporulated oocysts or ingests infected meat/tissue stages containing bradyzoites (slow multiplying stages). The human then ingests the bradyzoites; and they can then infect various tissue sites such as lymph nodes, meninges, eyes, and heart

Acquired

This infection is very difficult to diagnose and relies on demonstration of the organism or antibodies against it (blood tests that check for antibodies to the parasite). The best test is to inoculate the suspected material (blood) into mice and demonstrate the organism multiplying in the mice.

Toxoplasmosis

What is the treatment for Toxoplasmosis?

Pyrimethamine used in conjunction with triple sulfa drugs

What are the preventative measures that can be taken to avoid Toxoplasmosis?

1. Having someone else empty the cat’s litter box for the duration of
   pregnancy

2. Do not place litter boxes in kitchens or dining areas

3. Wash hands after handling a cat and before eating

4. Gloves should be worn while gardening, and hands should be washed after gardening is finished

5. Children sandboxes should remain covered when not in use

6. Cats should never be allowed to eat undercooked meat

7. Humans should not consume undercooked meat

This infection affects humans (particularly those with AIDS). It is reported in those who work with calves. It is spread by ingestion of infective oocysts in calf feces but can also be spread through contaminated drinking water. It causes transient, painful, watery diarrhea. It can last anywhere from 3-7 days (Acute cases) to a week - few months (Chronic). Most humans develop an immunity and recover from the infection although for those who are immunocompromised, the prognosis is poor.

Cryptosporidium parvum

What are ways that Cryptosporidium parvum can be diagnosed?

Fecal floatation + concentrating solutions and acid fast stains to identify the parasite. There are several ELISA tests and a commercially available indirect fluorescent antibody test.

What is the treatment for Cryptosporidium parvum?

fluid therapy and supportive care

What are the prevention methods for Cryptosporidium parvum?

1. Good sanitation and hygiene practices when handling young
   animals

2. Young children or immunocompromised individuals should not handle animals with diarrhea; and if they do handle pets they should be advised to wash their hands when they are finished (especially before eating)

3. Agents used to sanitize public drinking water have little effect on this organism

Human serve as incidental hosts for this parasite which comes form wild migratory birds and small mammals that are native to the water’s edge. It causes “Swimmers Itch” which is a highly pruritic skin condition that is caused by repeated penetration of the cercariae of schistosomes (blood fluke), it can persist for several days to a week and might become secondarily infected

Schistosomes of wild birds

What is the diagnosis of a Schistosomes of wild birds infection

Observation of the typical lesions in the skin which has been in contact with contaminated water

What is the treatment for a Schistosomes of wild birds infection?

Antihistamines and topical steroids; the hosts immune system will kill the cercariae which release an allergenic substance that causes the symptoms.

How do you prevent an Schistosome infection?

1. Do not swim in areas that have been
   posted with warnings on swimmer’s itch

2. Swim in water away from the shore
   reduces the chance of contact with the
   organism

3. If contact suspected, the swimmer should
   towel off immediately after leaving the
   water

4. For those who are working in water that
   are thought to be infective, protective
   waterproof clothing and repellants are
   available.

This effects humans who have ingested raw or undercooked meat of infected cattle. It causes a variety of nonspecific abdominal signs (diarrhea, constipation, and cramps) and the infected individual will pass about 10 gravid proglottids in the feces each day. It is known as the Beef Tapeworm

Taenia saginata

How is Taenia saginata diagnosed?

1. Proglottids in feces or finding eggs by performing perianal swabs and evaluating them

2. Diagnosis of cysticercus in cattle is usually made by meat inspections procedures

What is the treatment for Taenia saginata?

Praziquantel or Niclosamide

How is Taenia saginata prevented?

Inspecting meat; infected carcasses should be condemned for human consumption, and practicing good hygiene

This parasite infects humans who have ingested undercooked, infected pork. If a human if a human ingests of the eggs, they can hatch in the intestine —> penetrate the intestinal mucosa —> reach general circulation where it is distributed through the muscles, subcutaneous tissues, brain, and eye. Symptoms include a variety of nonspecific abdominal signs (diarrhea, constipation, and cramps); chains of gravid proglottids will pass in the feces each day. Other symptoms depend on parasite site (neurologic symptoms can include pain, paralysis, and epileptic seizures; ocular lesions may result in blindness). Common name is the Pork tapeworm

Taenia solium

How is Taenia solium diagnosed?

1. in pigs the cysticercus is usually identified during meat inspection

2. CT and MRI are used to reveal the parasite in human tissues (nervous system)

What is the treatment for Taenia solium?

Praziquantal; and surgical removal of lesions in humans

How do you prevent human cysticercosis of Taenia solium?

Personal hygiene, meat inspection, and not eating undercooked pork

This parasite affects humans that ingest the eggs. Its symptoms depend on the site that the organism is developing but pain, paralysis, and seizures have all been associated with the infection. If this is parasite is documented, STATE AND LOCAL OFFICIALS ARE TO BE NOTIFIED!!

Echinococcus granulosus and Echinococcus multilocularis

How is Echinococcus granulosus and E. multilocularis diagnosed?

CT and MRI will reveal the presence of the organism within the brain and other organs

What are the treatments for E. granulosus and E. multilocularis?

Surgical intervention; when unavailable, albendazole and mebendazole have shown some success

How do you prevent E. granulosus and E. multilocularis?

Handwashing; dogs never being fed raw livestock viscera or allowed to feed on wild rodents

This parasite affects children, particularly those under the age of 8 years old, who have ingested an infected flea. Most patients are asymptomatic, but diarrhea, abdominal pain, and anal pruritus may occur. It is diagnosed when proglottids are passed in the feces or found around the anus. It is treated by Prazinquantel and Niclosamide. It is prevented by flea control.

Dipylidium caninum

This parasite affects children, and sometimes adults, who have ingested infected insects. In light infections there are no significant damage or vague abdominal complaints, young children frequently have loose bowel movements or frank diarrhea with mucus, persistent abdominal pain, and pruritic anus, children can also experience headaches, dizziness, sleep disturbances, and behavioral disturbances. It is diagnosed by finding eggs on a fecal float and treated with prazinquantel. Personal and environmental hygiene are the best prevention methods.

Hymenolepis nana

This affects humans who have ingested lightly pickled, insufficiently cooked, or raw infected fish. Symptoms include nonspecific abdominal symptoms (abdominal pain, bloating, allergic reactions, hunger pains, loss of appetite, or increased appetite), in rare occasions it can cause mechanical intestinal obstruction, and may absorb vitamin B12 and produce anemia. It is diagnosed by seeing proglottids in feces or around the anus. It is treated with Prazinquantel and Niclosamide, and prevented by properly cooking freshwater fish and not feeding domestic animals raw fish.

Diphyllobothrium latum

This affects children and is caused by the Toxocara species when eggs are ingested from the soil, contaminated hands, or other objects. There are two distinct syndromes; visceral, in which the larvae migrate through the tissues and organs (liver, lungs, heart, and brain) (fatalities may occur when the myocardium or CNS are involved), and Ocular, in which the larvae invade the eye and is most common (faulty vision and blindness may occur).

Toxocaral larval migrans

This parasite is diagnosed based on the observation of lesions and the larvae in biopsy samples. There is no proven treatment available but mebendazole and diethylcarbamazine have been used; prednisone helps control the symptoms. To help prevent infection of this parasite, keep the places in which pets defecate clean, educate pet owners about this parasite, and have your cats and dogs routinely tested for intestinal parasites.

Toxocara species

This parasite affects humans who ingest eggs from raccoon feces, soil, contaminated hands, or objects. They migrate through the CNS caused sudden lethargy, loss of muscle coordination, decreased head control, ataxia, and nystagmus; they will progress to stupor, extensor rigidity, coma, and finally death. Diagnoses must be made on history, clinical findings, and serologic testing with a history of exposure to raccoons or their feces. There is no treatment for this parasite. Contaminated areas, cages, or traps should be decontaminated; access to known or potentially contaminated areas should be restricted. It causes neural larval migrans.

Baylisascaris procyonis

This affects humans, particularly children, plumbers, electricians, and travelers. Humans become infected when the larvae penetrate unprotected skin such as when people go barefoot in infected areas. It causes skin lesions which the severity of is related to the degree of exposure. It is diagnosed by the red, tunnel-like migration tracks with intense pruritus, blisters, and red bumps. It is treated with oral and topical treatments with thiabendazole and prevented by routine examinations of pets, covering of childrens sandboxes, and keeping areas clear of feces. They cause cutaneous larval migrans

Ancylostoma spp. and Uncinaria spp.

This is caused by Strongyloides stercoralis and affects humans (worse in immunocompromised people). Humans can be infected with this by coming in contact with infected dogs, cats, and other carnivores (they can penetrate the skin of a human and migrate to the intestine). Symptoms include coughing to severe pneumonia, diarrhea which can lead to exhaustion and emaciation (infection can be mild, severe, or cause death).

Strongyloidiasis

This is diagnosed by fecal smear, fecal float, or the baermann technique. It is treated with Ivermectin or Thiabendazole, and prevention for this is the same as that of the Toxocara species. It causes Strongyloidiasis.

Strongyloides stercoralis

This parasite causes Trichinosis and affects humans who have eaten lightly processed, partially cooked or raw pork (home raised or locally purchased swine are an important source). The severity of symptoms is related to the number of larvae ingested, and most cases are subclincal. Usually diagnosed in the muscle phase but can be diagnosed with serum chemistries and blood hemograms. It can be treated with Benzimidazole and prevented infeciton by thoroughly cooking pork

Trichinells spiralis

These are the two forms of symptoms that occur with a Trichinosis infection of Trichinella spiralis

Early abdominal syndrome (seen 2-7 days after infection (nausea vomiting, anorexia, mild fever, abdominal pain, or diarrhea)) and Later general trichinosis syndrome (seen weeks to months after the abdominal syndrome (cysts are found in the skeletal muscle which causes the infected individuals to develop muscle pain and weakness))

This affects humans who come into contact with infested dogs. Symptoms include lesions (papules or vesicles) on the trunk, abdomen, and arms (rarely seen on the face or genitals) that are extremely pruritic. This is diagnosed through observation of the typical lesions on the skin that has come in contact with an infested dog.

Sarcoptes scabei

What is the treatment for Sarcoptes scabei?

Antihistamines, topical steroids, and antibiotics

What are the preventative measures for Sarcoptes scabei?

Avoid contact with infested dogs and treat all dogs in the household