Virology Dr Sadia Ikram

Differences Between Viruses & Bacteria Property Viruses Cells Type of nucleic acid DNA or RNA but not both DNA and RNA Proteins Few Many Lipoprotein membrane Envelope present in some viruses Cell membrane present in all cells Ribosomes Absent Present Mitochondria Present in eukaryotic cells Enzymes None or few Multiplication by binary fission or mitosis No Yes

Viruses must reproduce within cells. Cannot generate energy or synthesize proteins. Reproduce only within cells (obligate intracellular parasites). Bacteria: obligate intracellular parasites chlamydiae and rickettsiae. Cannot synthesize sufficient energy to replicate independently.

DNA Viruses

RNA Viruses

Viral replication

Pathogenesis Four main effects of virus infection on cell: (1) death. (2) Fusion of cells to form multinucleated cells. (3) Malignant transformation. (4) No apparent morphologic or functional change.

Stages of a typical viral infection: Incubation period: Patient asymptomatic. Prodromal period: Nonspecific symptoms: Specific-illness period: Characteristic symptoms and signs occur. Recovery period: Illness wanes &patient regains good health. In some patients, the infection persists and a chronic carrier state or a latent infection occur.

Laboratory Diagnosis Five approaches to diagnosis of viral diseases: (1) identification of the virus in cell culture. (2) microscopic identification directly in the specimen. (3) serologic procedures to detect a rise in antibody titer or the presence of IgM antibody. (4) detection of viral antigens in blood or body fluids. (5) detection of viral nucleic acids in blood or patient's cells.

Microscopic Identification Inclusion bodies. Multinucleated giant cells. Serologic Procedures Presence of IgM: Diagnose current infection. Presence of IgG: Diagnose chronic infection

Major Viral Pathogens Structure Viruses DNA enveloped viruses Herpesviruses (herpes simplex virus types 1 and 2, varicella-zoster virus, cytomegalovirus, Epstein-Barr virus, human herpesvirus 8), hepatitis B virus, smallpox virus DNA nucleocapsid viruses Adenovirus, papillomaviruses, parvovirus B19 RNA enveloped viruses Influenza virus, parainfluenza virus, respiratory syncytial virus, measles virus, mumps virus, rubella virus, rabies virus, human T-cell lymphotropic virus, human immunodeficiency virus, hepatitis C virus RNA nucleocapsid viruses Enteroviruses (poliovirus, coxsackievirus, echovirus, hepatitis A virus), rhinovirus, rotavirus, Norwalk virus, hepatitis E virus

Hepatitis Viruses Five medically important viruses "hepatitis viruses" because their main site of infection is liver. Hepatitis A virus (HAV). ( Infectious hepatitis) Hepatitis B virus (HBV). Hepatitis C virus (HCV). Hepatitis D virus (HDV, delta virus). Hepatitis E virus (HEV). Epstein-Barr virus (the cause of infectious mononucleosis), cytomegalovirus, and yellow fever virus, infect liver and other sites in body and therefore not exclusively hepatitis viruses.

Hepatitis Viruses Virus Mode of Transmission Laboratory Diagnosis Vaccine Hepatitis A Virus Fecal-oral IgM HAV Yes Hepatitis B Virus Blood, sexual, at birth HBsAg, HBsAb, IgM. Hepatitis C Virus Blood, sexual HCV Ab No Hepatitis D Virus Ab to delta Ag Hepatitis E Virus None

Human Tumour viruses: Human T-cell lymphotropic virus: causing leukemias and lymphomas. Human papillomavirus: causing papillomas and squamous cell carcinomas. Epstein-Barr Virus: causing nasopharyngeal carcinoma. Hepatitis C Virus: causing hepatocellular carcinoma.

PARASITOLOGY Dr. SADIA IKRAM

What is Parasite and Parasitism A parasite is an organism that in lives and infects other living thing (host) and obtain shelter and nourishment from it. PARASITISM A form of symbiosis in which one organism (called parasite) benefits at the expense of another organism usually of different species(called host).

Definitions Host: “the organism in, or on, which the parasite lives and causes harm” Definitive host: “the organism in which the adult or sexually mature stage of the parasite lives.” Intermediate host: “the organism in which the parasite lives during a period of its development only. i.e. Asexual, immature form of parasite.” Zoonosis: “a parasitic disease in which an animal is normally the host - and the parasite also infects man” Vector: “a living carrier (e.g. an arthropod) that transports a pathogenic organism from an infected to a non-infected host”. A typical example is the female Anopheles mosquito that transmits malaria.

INTRODUCTION TO BASIC PARASITOLOGY Parasites are Eukaryotes. Two major groups: Protozoa (unicellular) Metozoa/Helminth (Multicellular) or worms

Important Groups of Human Parasites Protozoa Amoeba Flagellate Sporozoa Ciliate Helminthes Platyheminthes Trematodes Cestodes Nematodes Arthropoda Mosquito Fly Tick Mite Bug Flea Lice

CLASSIFICATION of HELMINTHS Platyhelminthes Flatworms are flattened, hermaphroditic, with a few exceptions Subdivided in to Two classes: Cestoda (tapeworms) &Trematoda (flukes). Cestodes, or tapeworms Taenia solium, Echinococcus granulosus. II. Trematoda (flukes) Fasciola hepatica, Clonorchis sinensis, Schistosoma spp. Fascioloa hepatica Taenia saginata

CLASSIFICATION of HELMINTHS b. Nematoda (roundworms) Elongated , round and un-segmented. Most human infections-ingestion of egg or larva. Examples Ascaris lumbricoides, Ankylostoma duodenale, Enterobius vermiculoaris etc

Clinical Classification of Protozoa Intestinal Entamoeba histolytica (Amoebiasis) Giardia lamblia (Giardiasis) Balantidium coli (Opportunistic infections) Isospora belli Cryptosporidium Vaginal Trichomonas vaginalis (Viginal infections) Blood – Plasmodium (Malaria) Leishmania (Kala Azar) Trypanosoma (Sleeping sickness) Tissue Toxoplasma gondii (Toxoplasmosis)

Direct Life Cycle Direct Life cycle Only humans are host Infective stage like ovum, cyst, larva passed out of body that infect healthy person. Example E histolytica, Giardia, Ascaris lumbricoides.

Indirect Life Cycle Indirect Life cycle Multiple hosts or involvement of vector. Definitive host, Intermediate host. Example Taenia saginata spp, Schistosoma spp etc Life cycle of Taenia saginata

Infective and Diagnostic stage Forms or stages of a parasite: Diagnostic Stage: Trophozoite: (active feeding, vegetative stage of a protozoal parasite). Infective Stage: Cyst/ oocyst: (inactive, dormant with protective thick wall, infective form).

Laboratory Diagnosis & Treatment Stool Examination Serology ELISA PCR Albendazole & Mebendazole.