Misshapened prion proteins carry the disease between individuals and cause deterioration of the brain. TSEs are unique diseases in that their aetiology may be genetic, sporadic, or infectious via ingestion of infected foodstuffs and via iatrogenic means (e.g., blood transfusion). Most TSEs are sporadic and occur in an animal with no prion protein mutation. Inherited TSE occurs in animals carrying a rare mutant prion allele, which expresses prion proteins that contort by themselves into the disease-causing conformation. Transmission occurs when healthy animals consume tainted tissues from others with the disease. In the 1980s and 1990s, bovine spongiform encephalopathy spread in cattle in an epidemic fashion. This occurred because cattle were fed the processed remains of other cattle, a practice now banned in many countries. In turn, consumption (by humans) of bovine-derived foodstuff which contained prion-contaminated tissues resulted in an outbreak of the variant form of Creutzfeldt–Jakob disease in the 1990s and 2000s.Prions cannot be transmitted through the air, through touching, or most other forms of casual contact. However, they may be transmitted through contact with infected tissue, body fluids, or contaminated medical instruments. Normal sterilization procedures such as boiling or irradiating materials fail to render prions non-infective. However, treatment with strong, almost undiluted bleach and/or sodium hydroxide, or heating to a minimum of 134 °C, does destroy prions. Classification
Features
The degenerative tissue damage caused by human prion diseases (CJD, GSS, and kuru) is characterised by four features: spongiform change, neuronal loss, astrocytosis, and amyloid plaque formation.
It has been shown in limited test studies that the nursing infant is exposed to approximately 0.3 mg/kg/day following oral administration of aciclovir to the mother. If nursing mothers have herpetic lesions near or on the breast, breast-feeding should be avoided. Adverse effects
Systemic therapy
Common adverse drug reactions (≥1% of patients) associated with systemic aciclovir therapy (oral or IV) include nausea, vomiting, diarrhea, encephalopathy (with IV use only), injection site reactions (with IV use only) and headache. In high doses, hallucinations have been reported. Infrequent adverse effects (0.1–1% of patients) include agitation, vertigo, confusion, dizziness, oedema, arthralgia, sore throat, constipation, abdominal pain, hair loss, rash and weakness. Rare adverse effects (<0.1% of patients) include coma, seizures, neutropenia, leukopenia, crystalluria, anorexia, fatigue, hepatitis, Stevens–Johnson syndrome, toxic epidermal necrolysis, thrombotic thrombocytopenic purpura and anaphylaxis.Intravenous aciclovir may cause reversible nephrotoxicity in up to 5% to 10% of patients because of precipitation of aciclovir crystals in the kidney. Aciclovir crystalline nephropathy is more common when aciclovir is given as a rapid infusion and in patients with dehydration and preexisting renal impairment. Adequate hydration, a slower rate of infusion, and dosing based on renal function may reduce this risk.The aciclovir metabolite 9-Carboxymethoxymethylguanine (9-CMMG) has been shown to play a role in neurological adverse events, particularly in older people and those with reduced renal function. Topical therapy
Aciclovir topical cream is commonly associated (≥1% of patients) with: dry or flaking skin or transient stinging/burning sensations. Infrequent adverse effects include erythema or itch.