Cat-scratch disease presenting as neuroretinitis and peripheral facial palsy

Rocky Mountain Spotted Fever (RMSF) is a severe tick-borne illness caused by Rickettsia rickettsii, a Gram-negative, coccobacillary bacterium. This pathogen is an obligate intracellular parasite, requiring a host cell for replication. Transmission occurs through the bite of an infected tick. In the United States, the most important vectors are Dermacentor variabilis (American dog tick) and Dermacentor andersoni (Rocky Mountain wood tick), though other tick species may also serve as vectors.

Rabies is a lethal zoonotic disease caused by a single-stranded, negative-sense RNA virus of the Lyssavirus genus, within the family Rhabdoviridae. Its primary mode of transmission to humans is through bites or saliva-contaminated scratches from infected mammals such as dogs, bats, raccoons, or foxes. Transmission can also occur if infectious saliva contacts abraded skin or intact mucous membranes, including the conjunctiva.Viral Entry and Early ReplicationOnce introduced at the bite or scratch...

Arboviral encephalitis refers to brain inflammation caused by arthropod-borne viruses, particularly those transmitted through mosquito vectors. Among these, West Nile virus (WNV), a member of the Flaviviridae family, is a significant public health concern. WNV is an enveloped, positive-sense, single-stranded RNA virus. Human infection typically begins when an infected mosquito introduces the virus into the dermis during feeding. The primary transmission cycle involves birds as amplifying hosts...

Toxoplasmosis, a zoonotic disease caused by the protozoan Toxoplasma gondii, poses significant public health challenges globally due to its high seroprevalence and varied clinical manifestations. As an obligate intracellular parasite, T. gondii can infect all warm-blooded vertebrates, but felids are its only definitive hosts, shedding unsporulated oocysts into the environment. Humans typically acquire the infection through ingestion of tissue cysts in undercooked meat or oocysts from...

Encephalitis is inflammation of the brain parenchyma caused by direct viral invasion or immune-mediated mechanisms triggered by infections or tumors. Both processes lead to neuronal injury, disrupted neurotransmission, and diverse neurological symptoms, often with overlapping clinical and pathological features.Autoimmune EncephalitisIn autoimmune encephalitis, antibodies target neuronal antigens on cell surfaces, synapses, or within neurons. A key example is anti-NMDAR encephalitis, which can...

Multiple sclerosis is a chronic autoimmune disease of the central nervous system (CNS) that affects the brain, spinal cord, and optic nerves. It is an inflammatory demyelinating disorder and a leading cause of neurological disability in young adults.EpidemiologyMS commonly begins between 20 and 40 years of age and is twice as common in women. Its exact cause remains unclear, but genetic susceptibility contributes, with higher risk in first-degree relatives and identical twins. A greater...