Dr. S. S. DasProfessor and Head

Department of Veterinary ParasitologyRIVER, Pondicherry

(Toxon: Arc , Plasma: form)

Taxonomical classification

Kingdom- ProtistaSubkingdom- ProtozoaPhylum- ApicomplexaClass- SporozoasidaOrder- EucoccidioridaFamily- SarcocystidaeGenus- ToxoplasmaSpecies- Toxoplasma gondii

History➢ Toxoplasmosis is a Zoonotic disease, caused by Toxoplasma gondii, an

obligate intracellular parasite.

➢ Toxoplasma gondii was first discovered in 1908 by Nicolle and Manceaux, in Tunis, in an African rodent (Ctenodoactylus gundi).

➢ 1939 that Wolf, Cowen and Paige observed that Toxoplasma gondii had an effect on humans.

Ctenodoactylus gundi

➢ The feline is the only definitive host, but other warm blooded animals, including humans, can serve as an intermediate host.

➢ No discrimination on sex, age or species. However it is rare in dogs.

➢ Toxoplasmosis is a world spread disease.

Alone in the US around 60 million people carry the toxoplasmaparasite without even showing symptoms.

It is a big concern for pregnant women, and immune-compromised people.

➢ It occurs in two forms-

➢ 1. Intestinal or enteroepithelium in cats and

➢ 2. extraintestinal phase in cats and other warm blooded

animals.

Toxoplasmosis facts

Continuation of Toxoplasmosis facts

•Toxoplasma gondii are present in any nucleated cells of warm blooded animals.

•They causes abortion in woman, ewe and doe.

•It does not cause any abortion in cats because they have coronary placentation wherein the transplacental transmission is not possible.

➢ Toxoplasmosis is caused by ingesting contaminated vegetables,

water, fruit and undercooked/raw meat.

➢ By ingesting contaminated feces, for example after cleaning out

a litter box.

➢ Or by doing garden work, and not maintaining a healthy hand

washing regime.

What causes Toxoplasmosis

Signalment

➢ Toxoplasmosis is found in most warm blooded animals of any age, sex or species.

➢ The feline is the only definitive host, but humans and other animals can serve as an

intermediate host.

➢ In the US it is the leading food-born disease causing death.

➢ It can be very detrimental for pregnant women or animals, causing abortions

around the 3rd trimester.

➢ Toxoplasmosis is zoonotic

➢ Transmission can occur in 3 ways

• Fecal-oral

▪ Eating contaminated meat/prey

▪ Transplacental

➢ The parasite can only produce oocytes (or eggs) when infecting a cat. The organism then multiplies in the wall of the small intestine and produces oocysts during the enteroepithelium infection cycle.

Transmission

➢ There are three forms of Toxoplasma gondii

Tachyzoite – Rapidly reproducing form

Bradyzoite – A slower reproducing form, contained in tissue

Sporozoite – Contained in oocysts

➢ Toxoplasma gondii have two forms of cysts namely true cyst and pseudocyst.

➢ Tachyzoites are also called as aggregration of colony or pseudocyst since they lack cyst wall.

➢ They have prominent centrally placed nucleus.

➢ They are crescent shaped.

➢ They multiply by endodyogeny or endopolygeny process of asexual multiplication.

➢ Tachyzoites invade cells in the body in order to multiply. They invade a cell, multiply themselves rapidly, destroy the cell, and this releases more tachyzoites to infect other cells.

➢ .

Tachyzoite

➢Tachyzoites are seen in many tissues and organs throughout an infected body during the acute phase of the disease.

➢The acute phase is also called the extraintestinal phase because it can effect cells outside the intestines.

➢It can infect phagocytic and nonphagocytic cells.

➢Only cats show the intestinal phase of the infection.

➢Tachyzoites are present when the host immune response slows down.

➢Once the host immune system increases , tachyzoites develop into bradyzoites

Tachyzoites

Stained tachyzoites

Two or three weeks after the first infection, the Toxoplasma

microorganism begins to divide more slowly and a protective

membrane forms around the parasite cells.

➢ This marks the chronic. phase of infection

➢ The cysts containing the parasite cells are called zoitocysts and

the cells inside the cysts are called bradyzoites

➢ They have cresent shaped structure.

➢ Bradyzoites are resisitent to low pH,digestive enzymes during

stomach passage.

➢ Nucleus is in terminal position.Glycogen granules are present

unlike tachyzoites where the glycogen granules are absent.

➢ The tissue cysts are formed primarily in brain, eye, heart muscle,

and skeletal muscle.

➢ Bradyzoites persist in tissue for many years, possibly for the life

of the host.

Bradyzoites

Bradyzoite

BRADYZOITE

BRADYZOITE

TISSUE CYST

THE OOCYST

• The oocyst is noninfectious before sporulation.

• Unsporulated oocysts are subspherical to spherical.

• Sporulated oocysts are subspherical to ellipsoidal.

• Each oocyst has two ellipsoidal sporocysts.

• Shedding occurs 3-5 days after ingestion of tissue cysts

• Sporulated oocyst remain infective for months .

Sporulated oocysts

Unsporulated oocysts

Two sporocysts

➢ In cats, the Toxoplasma parasites infect the lining of the small intestine where they reproduce sexually.

➢ Approximate diameter of oocyst – 10 µm.

➢ After a few days of rapid reproduction the cells transform into a

sexual form, combine, and become enclosed in a cyst called an

oocyst which is of Isosporan type(2 sporocyst with 4 sporozoites each)

➢ Oocysts contain the sporozoite form of the Toxoplasma parasite.

➢ Oocysts are found in both wild and domestic cats but not in any

other animals or birds.

➢ Unsporulated oocyst appears in the cat's feaces 3-5 days after feeding of Toxoplasma cyst.

➢ Oocyst requires oxygen and they sporulate within 1-5 days.

Oocysts

➢ Animals become infected by ingesting food contaminated with oocysts from feces or with tissue cysts (bradyzoite) from the flesh of infected animals.

➢ Infected cats shed millions of oocysts in their feces during the two-week period of the intestinal phase of the infection (i.e., when asexual reproduction of the Toxoplasma microorganisms occurs).

➢ These oocysts can survive in soil for several months and are the major source of infection.

➢ Once swallowed, the oocyst burst in the intestines and spreads to the rest of the body through the bloodstream.

➢ Sometimes arthropods also acts as tranport host

➢ Toxoplasmosis can be of acquired or congenital type of which the latter accounts for 98% of toxoplasmosis.

Oocysts cont.

FeverAnaemiaRespiratory distressPneumoniaSerosanguineous fluids

Hemorrhagic diarrheaIntestinal ulcers

▪Respiratory distress- dyspnea, coughing, sneezing, nasal discharge, pneumonia.▪Serosanguineous fluids▪Focal lesions in brain, lung , lymph node▪Fever, sudden death▪Chronic cases- Calcification of endothelial lining of blood vessels is common.

❖Cats are usually asymptomatic.❖However enteritis, lymph adenoma, pneumonia, nephritis may develop.

PATHOLOGY IN CATS

PATHOLOGY IN DOGS

PATHOLOGY IN CATTLE

✓Pericarditis

✓Focal or diffused myocarditis

✓Encephalomyelitis

•Congenital defects and abortion.•Severity of congenital infection depends upon the stage of infection.•Ewes aborted in one year gives birth to normal lambs in subsequent year due to development of immunity.

PATHOLOGY IN SHEEP

PATHOLOGY IN HORSES

PATHOLOGY IN BIRDS

Pathologic lesions of diseaseEYE

➢ Fever

➢ Loss of appetite

➢ Lethargy

➢ Other symptoms may occur depending on whether the infection is acute or chronic, and location in the body where the parasite is found.

➢ In cats it is most commonly seen effecting the lungs and eyes.

➢ And in the dog, the gastrointestinal, neurological and the respiratory system.

Clinical signs & symptoms

CLINICAL SIGNS AND SYMPTOMS CONT.

•Symptoms in congenital toxoplasmosis

•Ocular lesions•Neurological involvement•Hydrocephalus•Vision problem•Intracerebral calcification•Convulsion•Mental retardation•Cardiomegaly.

Infection in early pregnancy results in low transmission but severe diseases while that of late pregnancy results in high transmission with benign symptoms.

HYDROCEPHALUS

➢ History

➢ Faecal examination in cats.

➢ ELISA

➢ Serology testing – measuring the IgM & IgG anti-bodies

➢ Sabin-Feldman Dye Test (DT)

➢ Differential agglutination test (also known as the "AC/HS test")

Diagnosis

➢ Pyrimethamine + sulfa drugs: 120 mg/kg : 1mg/kg

➢ For an immune-compromised animal a 2-3 week treatment of clindamycin isaffective.

Treatment

➢ For healthy animals and humans the prognosis is good. The disease should be hibernating and not causing any damage.

➢ For individuals with weakened immune systems, the prognosis is not good. The disease has to be kept down with medicine, and complications can occur depending or what tissues of the body are being effected.

➢ For example, if toxoplasmosis is effecting the eye, the body will try and attack the foreign invader, which can lead to blindness.

➢ Immune-compromised hosts infected with toxoplasmosis may have encephalitis, pneumonitis and myocarditis as manifestations of the infection.

➢ These infections are usually fatal if not recognized and treated.

Prognosis

➢ Avoid eating raw meat, unwashed fruit and vegetables

➢ Keep children's sand boxes covered.

➢ Wash hands after dealing with raw meat, gardening, and changing litter boxes.

➢ Change litter boxes daily (the oocytes shedded in the feces don't become infectious for 1-5 days)

➢ Don't feed animals raw meat.

➢ If pregnant wear gloves when changing litter boxes, and keep cats indoors to insure they don't hunt and eat contaminated prey/meat.

➢ There is only one vaccine available. It is exclusively for sheep and it is only approved for use in Great Britain

➢ Do not allow animals to eat raw meat

➢ Properly cooked food above 65 c

➢ Pregnant lady shouid avoid contact with cat/ cat faeces

Prevention