Transfusion Transmitted Infections (TTIs)

Blood transfusion is the process of receiving blood or blood products intravenously
Transfusions are used to replace lost blood components or as a therapy
TTIs are infections resulting from the introduction of a pathogen into a person through blood transfusion

Outline measures blood banks use to decrease the risk of TTIs
Recognize criteria for blood donation and causes of rejection
Outline factors that contribute to TTI establishment
Identify common TTI pathogens and describe their morphology, classifications, modes of transmission, pathogenesis, and diagnostic methods

RNA Viruses: HIV, HTLV, HCV
DNA Viruses: HBV, Epstein-Barr virus, Cytomegalovirus (CMV), Human Herpesvirus 8 (HHV-8), Parvovirus B19
Protozoa: Plasmodium, Toxoplasma
Bacteria: Bacterial contamination
Treponema: Treponema pallidum (causes syphilis)
Prions: 72 currently known agents

Standard donor screening questionnaire
Screening of donated blood:
- PCR
- Bacterial culture
- Antigen and antibody detection
- Test for specific organisms such as HBV, HCV, HIV, HTLV, and syphilis
Pathogen inactivation technique: treating blood components with chemicals and/or UV light to inactivate infectious agents

Viral Window Period: the period between acquiring a viral infection and its detection by laboratory tests; includes false-negative results and varies between days and 6 months, e.g., HIV window period is 11-180 days
Bacterial contamination
Asymptomatic immunocompetent donors
Laboratory errors
Personal errors

Virology: Enveloped, single-stranded RNA virus
Classification: Retroviridae family, HIV-1 and HIV-2 species
Transmission: Sexual transmission, parenteral (blood transfusion, needle stick injury, sharing needles), tissue transplantation, vertical (pregnancy, childbirth, breastfeeding)
Replication Cycle: Adsorption (to helper T cells, macrophages, dendritic cells), Uncoating (viral RNA release), Conversion of viral RNA to DNA, Integration of viral DNA into cellular DNA, Transcription and protein synthesis, Assembly, and Release by budding

Virology: Single-stranded, enveloped RNA virus
Classification: Retroviridae family
Target Cells: T helper cells
Cause: adult T-cell leukemia and lymphomas
Transmission: Sexual route, vertical transmission (breastfeeding), and blood transfusion

Virology: Enveloped, single-stranded RNA virus
Cause: Hepatocellular carcinoma (liver cancer)
Transmission: Parenteral (needle sharing, needlestick, blood transfusion, dialysis, organ transplantation)

Virology: Double-stranded, icosahedral DNA virus
Presence: Complete infectious viruses, filamentous and spherical bodies without a core
Forms: Hepatitis B surface antigen (HBsAg)
Cause: Hepatocellular carcinoma
Transmission: Sexual, parenteral (contaminated needles/instruments), organ transplants, vertical transmission (during birth)
Prevention: Vaccine made of surface antigen (HBsAg)

Virology: Enveloped DNA virus
Classification: Herpesviridae family
Transmission: Body fluids (especially saliva), blood transfusion, organ transplantations, and sexual contact
Causes: 90-95% of adults are seropositive (have antibodies)
Pathogenesis: Infects epithelial cells of the oropharynx, then B lymphocytes; uncontrolled function leads to heterophile antibodies; Hyper activation of T cells → atypical T lymphocytes (Downey cells); Uncontrolled multiplication → lymphomas, Latency and reactivation → shedding of EBV in saliva → infecting others
Disease: Infectious mononucleosis (glandular fever)
Complications: Splenic rupture (activity restriction, avoid trauma), Lymphomas, Nasopharyngeal carcinoma
Diagnosis: Monospot test to detect heterophile antibodies; Peripheral smear: lymphocytosis (>10% atypical lymphocytes in some cases up to 90%); PCR to detect viral DNA; Serology: anti-EBV antibodies

Virology: Enveloped DNA virus
Classification: Herpesviridae family
Transmission: Body fluids (especially saliva), sexual, vertical (transplacental, during birth, breastfeeding), blood transfusion, tissue transplantation
Complications: immunocompromised individuals (interstitial pneumonitis, retinitis, encephalitis, colitis)

Virology: Non-enveloped, icosahedral, single-stranded DNA virus
Transmission: Inhalation, vertical (during birth), and blood transfusion
Pathogenesis: Replication in upper respiratory tract, spread to bone marrow, killing erythroid precursor cells
Complications: Fetus (severe anemia, abortion); Children (erythema infectiosum, slapped cheek disease); Adults (polyarthritis), Patients with chronic hemolytic anemia (e.g., sickle cell anaemia) – Aplastic crisis

Due to improper donor skin disinfection, contaminated donation equipment or donor bacteremia
Reduction methods:
- Skin disinfection with chlorhexidine and/or alcohol or iodine and alcohol
- Gram staining and blood culture

Bacteriology: Thin spirochete with Gram-negative cell wall and axial filaments (endoflagella)
Transmission: Sexual contact, vertical transmission (during birth), blood transfusion
Diagnosis: Cannot be cultured in vitro, Identification methods include: PCR, darkfield microscopy, immunofluorescence, light microscopy (silver stain) and serology (anti-cardiolipin/anti-treponema antibodies by TPHA test)

Etiology: P. vivax, P. malariae, P. ovale, P. falciparum
Classification: Sporozoa, obligate intracellular protozoa
Transmission: Bite of infected female Anopheles mosquito, transplacental, and blood transfusion
Pathogenesis: Infect hepatocytes and red blood cells (RBCs)
Diagnosis: Rapid antigen, Microscopy (stained blood film), stages of plasmodium (ring stage, schizonts, gametocytes)

Classification: Sporozoa, obligate intracellular protozoa (obligate parasite)
Transmission: Oral ingestion of oocysts (from cat feces, contaminated food/water) and tissue cysts (raw/undercooked meat)
Complications: Asymptomatic in immunocompetent individuals (~90% asymptomatic). Mononucleosis-like symptoms. Latent infection. Fetus and immunosuppressed patients with disease affecting the brain, eyes, lungs, heart, other organs

Specific organisms' classification and transmission methods
Overview of different disease types (infectious mononucleosis, Kaposi's sarcoma, etc.)
Diagnosis of specific infectious diseases.
List of preventative measures against TTIs