Leishmania donovani ___________________

Charles Louis Alphonse Laveran                                                        France Institute Pasteur Paris, France 1845 - 1922 The Nobel Prize in Physiology or Medicine 1907 "in recognition of his work on the role played by protozoa in causing diseases"

Leishmaniasis is prevalent world wide: ranging from south east Asia, Indo-Pakistan, Mediterranean, north and central Africa, and south and central America.

Species Pathogenic in Humans Leishmania donovani (Laveran 1903) (VL) Leishmania tropica (CL) Leishmania major (CL) Leishmania aethiopica (CL) Leishmania mexicana (CL) Leishmania brazilliensis (MCL)

Morphology Promastigote Amastigote Digenetic Life Cycle Insect Motile Midgut Amastigote Mammalian stage Non-motile Intracellular

Morphology Amastigote (leishman-donovan body): Human phase, reside in macrophage Very, very minute elliptical body No free flagellum Nucleus: deep red, located at one side Cytoplasm: blue (after right stain) Kinetoplast; basal body; rhizoplast

elongate form - 15 - 30 µm long Promastigote elongate form - 15 - 30 µm long one nucleus, red stained, central in position, one anterior flagellum which is just as long as its body length. a rod-like kinetoplast a dot-like basal body anterior Flagellum Basal body Kinetoplast Nucleus posterior Insect Motile Midgut

Promastigote: Vector phase Reside in the gut of sandfly Spindle shaped with 1 free flagellum Nucleus; cytoplasm; kinetoplast; basal body; rhizoplast Chrysanthemum-like in culture medium

A macrophage filled with Leishmania amastigotes.

Amastigote of L. donovani (under oil immersion objective)

Amastigote M broken with the release of amastigote which may invade other M, start asexual multiplication again

Promastigote Fusiform -shaped with 1 free flagellum Usually gather together in the medium as a mum

Promastigote

Electron photomicrograph of promastigotes

promastigote mum (under electron microscope)

Sandflies

Phlebotomus ，sandfly Small，about 1/3 of a mosquito, 3mm, yellow-gray

Life cycle

Life Cycle of Leishmania spp. _________________________________________________________

Promastigote Amasitgote Life Cycle Promastigote Amasitgote Transformation

Main points of the Life Cycle 2-host pattern, mammal insect vector (sandfly) Asexual multiplication occurred either in macrophages or in insect , No sexual development in the host infective stage: promastigote mode of infection:  biten by sandfly site of habitation:  macrophages pathogenic stage:  amastigotes diagnostic stage:  amastigotes reservoir host: dogs and rodents

Leishmania donovani PATHOLOGY: Amastigotes multiply in macrophage, destroyed the macrophage eventually rupturing the cell Free amastigotes then invade the circulatory system.

Parasite Spread Macrophage lysis & parasite release Target organs 1. Lymphatic spread 2. Blood spread Target organs the mononuclear macrophagocyte system of the spleen, liver, bone marrow and lymph nodes

Clinical features Lack of acquired immunity but may gain sterilizing immunity after effectively cured. Most severe form of the disease, may be fatal if left untreated, Reason: lack of immunity after infection. Irregular fever for long period is due to the broken piece from parasitized tissue. Massive hypertrophy of spleen , liver and lymph nodes are caused by the proliferation of mononuclear macrophagocytosis system. Destruction, hyperfunction

Clinical features Because bone marrow is involved and spleen is hyperfunction, caused anemia. The number of red blood cells( RBCs), white blood cells (WBC) and platelet all decrease. Bleeding results from the decrease in blood platelets. The decrease of liver function and the proliferation of plasma cells bring about the ratio of albumin to globulin is inverted. Skin lesions – granulomatous response: painless nodules in which amastigote may be found – sometimes self-cured Nephrosis: IC deposition –type III hypersensitivity. Emaciation with ascites, darkened skin, fever, bleeding of the gums, immunity decrease. Die of infective complications( noma, Pneumonia).

Clinical Disease Visceral Cutaneous Fatal (90% untreated) Liver Spleen Bone marrow Cutaneous Generally Self- healing Skin Mucous membranes

Profile view of a teenage boy suffering from visceral leishmaniasis. The boy exhibits splenomegaly, distended abdomen and severe muscle wasting. 

Two children with visceral leishmaniasis Splenomegaly

Enlarged spleen and liver in an autopsy of an infant dying of visceral leishmaniasis.

Jaundiced hands of a visceral leishmaniasis patient. 

Special clinical features for Kala-azar cases Post-kala-azar dermal leishmaniasis (PKDL)：

Cutaneous leishmaniasis of the face.

A cutaneous leishmaniasis lesion on the arm.

Cutaneous leishmaniasis

Diagnosis Etiological examination Puncture smear: bone marrow – safe, first choice Skin biopsy Tissue or aspirate cultivation Animal inoculation

Molecular biology methods Immuno-diagnosis Antibody detection Circulation antigen detection Molecular biology methods DNA probe test PCR

Treatment Injection of Antimony Gluconate cure rate would be 97.4％ Good nursing Pentamidine or stilbamidine for antimony-resistant patients Antibiotics Spleen excision

Epidemic Links Source of infection: patients and dogs Route of infection: sandfly. Susceptible population: all human beings ( but potent immunity developed after cure)

Prevention Treat the patients Suppress the reservoir: dogs, rats, other small mammals and rodents Suppress the vector: Sandfly Prevent sandfly bites: Personal Protective Measures

Trichomonas vaginalis (阴道毛滴虫) Trichomonas vaginalis, a flagellate, is the most common pathogenic protozoan in the countries. It causes trichomoniasis (毛滴虫病). The infection is transmitted sexually.

Morphology Pear-like in shape, about 10-30x5-15um in size. four anterior flagella and One posterior flagellum which attaches to pellicle to form an undulating membrane (波动膜). One nucleus the axon project posteriorly out of the body. The motility is jerky & non-directional.

Trichomonas vaginalis

Life cycle: Simple: Only Trophozoite stage. There is no cyst stage. Binary fission of reproduction.

Inhabitation: Female – Vagina(阴道) , Urethra（尿道）; Male – Urethra （尿道）, Prostate glands. Cause Trichomonas vaginitis, urethritis or prostatitis, i.e. Trichomoniasis.

Diagnosis 1. Etiological examination The specimen should be obtained from vaginal discharge, prostatic fluid or urine. Normal direct smear may be used for exam. the trophozoites. The typical robust Trichomonas can be seen because of their characteristic jerky motion moving among the epithelial cells. 2. PCR & DNA probe

Treatment Metronidazole is the drug of choice for both female & male. Sexual partners should be treated at same time.

Epidemiology Like most sexually transmitted diseases, trichomoniasis is prevalent in the sexually active age group in all climates and racial groups. New born girls appear to be at special risk of acquiring trichomoniasis from an infected mother during passage through the birth canal.

Although the organism died rapidly when dried , exposed to direct sunlight, person to person transmission may occur where there is a lack of sanitary toilets or bathing facilities and a sharing of contaminated clothing or washcloth.

Control 1. Treat patients & Carriers. 2. Pay attention to personal hygiene. 3. Avoidance of sexual contact with infected partners .

opportunistic protozoa opportunistic protozoa can not infect persons with normal immune mechanisms or can cause mild (or latent) infection with asymptomatic to self-limited symptoms . opportunistic protozoa may cause devastating disease in persons whose immune resistance has been weakened by various causes, such as:

immune deficiencies: eg. AIDS Malnutritions Malignancy 恶性肿瘤 Immunosuppresive medications: eg. organ transplantations Homosexuals

Toxoplasma gondii (toxoplasmosis)

Introduction Toxoplasma gondii has very low host specificity, and it will probably infect almost any mammal. It invades all kinds of cells except RBC Cats are the only definitive hosts and can also be the intermediate hosts The disease that Toxoplasma gondii caused (toxoplasmosis) has been found in virtually every country of the world Toxoplasmosis is a significant cause of morbidity and mortality in AIDS patients and congenitally infected infants -- opportunistic infection for human

Toxoplasma is an obligate intracellular parasite Toxoplasma is an obligate intracellular parasite.  Its life cycle includes two phases called the intestinal and extraintestinal phases. The intestinal phase occurs in cats only and produces "oocysts."  The extraintestinal phase occurs in all infected animals (including cats) and produces "tachyzoites" and, eventually, "bradyzoites" or "zoitocysts."  The disease toxoplasmosis can be transmitted by ingestion of oocysts (in cat feces) or bradyzoites (in raw or undercooked meat).

In most humans infected with Toxoplasma, the disease is asymptomatic In most humans infected with Toxoplasma, the disease is asymptomatic.  However, under some conditions, toxoplasmosis can cause serious pathology, including hepatitis, pneumonia, blindness, and severe neurological disorders.  This is especially true in individuals whose immune systems are compromised (e.g. AIDS patients).  Toxoplasmosis can also be transmitted transplacentally resulting in a spontaneous abortion, a still born死产, or a child that is severely handicapped mentally and/or physically.

Morphology There are five forms in T. gondii life cycle: trophozoite (tachyzoite, 速殖子), tissue cyst (bradyzoite, 缓殖子), schizont (裂殖体), gametocyte (配子体) and oocyst (卵囊).

Life Cycle

The tachyzoites directly destroy host cells Pathogenesis The tachyzoites directly destroy host cells

Clinical features Acquired toxoplasmosis Congenital toxoplamosis

Congenital Toxoplasmosis (1) malformation of fetus (birth defect) (2) abortion, premature delivery and stillbirth

Acquired Toxoplasmosis the tachyzoites destroy tissues, causing extensive lesions in the lung, liver, heart, brain and eyes. Symptoms: fever, headache, muscle pain, swollen lymph glands

In immunocompromised individuals, T. gondii infection results in generalized parasitemia involvement of brain, liver lung and other organs, and often death.

Diagnosis Microscopic Examination Animal Inoculation Serological tests -Smears and Sections Animal Inoculation Serological tests PCR & DNA probes

Epidemiology This disease is widespread and clinically important throughout the world. Human infections result from eating raw meat. Lots of mammals can serve as reservoir hosts.

Reasons of epidemic Source of oocysts ... domestic and wild cats, passes tons of oocysts Persist in environment if moist reservoir of infective oocysts Many intermediate hosts with infective stage reservoir of infective tissue cysts

Pneumocystis carinii Pneumocystis jiroveci (pronounced as "yee row vet zee")

Introduction Pneumocystis jiroveci has a world-wide distribution and the transmission seems to occur by airborne route. Pneumocystosis is one of the most common infections in immunosuppressed patients.

Morphology Trophozoites and cysts are the two main stages in the life cycle Life cycle Not yet completely clear

Cryptosporidium spp.

Introduction A threat to the quality of surface water and the environment...! Cryptosporidium is a protozoan parasite in water environment Causal agent of acute diarrheal disease in human and animals -- zoonosis Potentially lethal for immunosuppressed individuals

Diagnosis Stool examiniation for oocysts Biopsy of the intestine epithelium ！！Multiple stool samples (at least 3) should be tested before a negative diagnostic interpretation is reported