Rabies Virus: Study Notes

• Study notes for various microbes, viruses and diseases

Rabies Virus

• Most common in Africa and Asia
• Vectors can be dogs world-wide, plus wildlife in the USA (skunks, foxes, coyotes, bats) and jackals, foxes, and mongoose in Africa.
• Primarily transmitted through a bite from saliva of infected animal
• Other forms of transmission are exposure of mucous membrane, inhaling aerosolized virus, and organ transplantation
• Clinical symptoms are hyperactivity, disorientation, bizarre behavior, hypersalivation, sweating, and hydrophobia.
• Paralytic rabies leads to ascending symmetric paralysis with flaccidity, and decreased tendon reflexes.
• Post mortem diagnosis is standard to detect rabies virus antigen using a fluorescent antibody testing
• Histopathology may reveal Negri bodies in cytoplasm of undamaged nerve cells.
• Incubation period is asymptomatic
• Can resemble tetanus, typhoid, malaria, or other viral encephalitis
• Furious or paralytic rabies symptoms can occur
• Rabies is almost uniformly fatal once apparent
• Pre-exposure vaccination for high-risk individuals and post-exposure prophylaxis (PEP) after potential exposure are options
• PEP includes washing the wound with soap and water, virucides, rabies vaccine and rabies immunoglobulin

Salmonellosis: Bacterial Infection caused by Salmonella bacteria

• Location of cases in USA is California, New York, and Texas
• Found in the gut flora of turtles and is shed in their stool, heavily contaminating their environment
• Primarily turtles, but livestock animals such as pigs, cows, sheep, and goats can also be vectors
• Can be transmitted by exposure to turtles or their environment
• Fecal oral transmission and consumption of contaminated food products are other routes of exposure
• 29% hospitalization rate
• Prevention includes banning the sale of small turtles (less than 10.2 cm or 4 inches in length) and good hygiene practices
• Thorough cooking of food is also a preventative measure
• Incubation is typically 20-90 days, but in rare cases can be range from less than 30 days to over a year, and in rare cases: long as 14-19 years

Mycobacterium tuberculosis (MTB)

• Primarily infects humans, but animals can incidentally be infected
• Spread person to person by respiratory droplets or animals can be infected through reverse zoonosis
• Clinical presentation is coughing (for three or more weeks), coughing up blood, chest pain, unintentional weight loss, fatigue, fever, chills, and loss of appetite
• DNA-based techniques (MTB PCR) allow for fast differentiation of Tb from NTM

Nontuberculous Mycobacteria (NTM)

• Ubiquitous (found everywhere) in the environment and rarely causes disease
• Pulmonary disease is most common, along with superficial lymphadenitis, disseminated disease (MAC in HIV), and skin and soft tissue infection through immunization/vaccine
• Acid-fast microscopy with fluorochrome stains and DNA-based techniques (MTB PCR) can be used
• Culture remains the gold standard for identification

Mycobacterium Bovis

• Human to human transmission is rare
• The main host is cattle can infect a wide range of wildlife
• Can spread to humans through inhalation of infectious droplet nuclei and ingestion of raw milk, or by direct contact with bodily secretions or consumption of infected animal products
• Pulmonary disease is indistinguishable from M. tuberculosis disease
• Resistant to pyrazinamide
• Treatment involves 2 months of isoniazid, rifampin, and ethambutol, followed by 7 months of isoniazid and rifampin
• Prevention is pasteurization of milk, and bovine eradication schemes

Mycobacterium avium complex (MAC)

• Birds are a primary reservoir, spreading it in their feces
• Acquired from the environment via aerosolized water, soil exposure, and showerheads
• Disseminated in immunocompromised hosts
• Cervical lymphadenitis occurs in children
• Symptoms include chronic cough, fever, chills, night sweats, dyspnea, hemoptysis, and weight loss
• Seen in blood cultures
• Treatment is extremely difficult
• Treatment includes daily clarithromycin/azithromycin + rifampin/rifabutin + ethambutol
• Streptomycin may be added 2-3 times per week for the first 2 months, especially if there is extensive cavitary disease
• Treatment should continue for at least one year after the culture is negative
• Preventions include MAC prophylaxis in HIV-infected patients with CD4 <50 and/or rifabutin 300 mg/day
• Prophylaxis may be discontinued when patients respond to HAART with CD4 >100 for >3 months.

Mycobacterium marinum

• Found in aquariums, freshwater or saltwater
• Free-living bacterium found in fish
• Transmitted through trauma to the skin in contaminated nonchlorinated fresh or saltwater
• Causes cutaneous disease with a single violet papulonodular lesion that may ulcerate, with secondary nodules along the lymphatics

Mycobacterium leprae (leprosy)/lepromatosis

• Worst-hit in Brazil, India, Nepal, Tanzania, and Mozambique

• M. lepromatosis + mycobacterium leprae are found in armadillos

• Vector (Host): Southern US armadillos are naturally infected with M. leprae

• M. leprae transmission is unclear but suspected to be through prolonged close contact and nasal droplets

• Results in skin lesions and neuropathy, particularly in cold, peripheral locations, leading to nerve demyelination

• Lepromatous leprosy presents with numerous skin lesions and a high bacterial load

• Tuberculoid leprosy is characterized by a cell-mediated immune response

• Lepromatous form involves histopathologic findings and microscopy, and skin testing Tuberculoid form involves histopathological findings and skin testing Note that leprosy presentation must be distinguished from diabetic neuropathy

• M. leprae cannot be grown in cell-free cultures for diagnosis

• M. lepromatosis infects peripheral nerves (acid-fast, non-cultivable)

• The lepromatous form involves using rifampin, dapsone, and clofazimine for 12 months.

• The tuberculoid form involves using rifampin and dapsone for 6 months.

Mycobacterium simiae

• Has been isolated in humans in Europe, USA, and Asia
• First isolated from healthy Macaques rhesus (monkeys) imported from India
• Transmission has been observed between animals in captivity and also from animals to humans

Psitaccosis

• Organism is Chlamydia psittaci
• Birds are reservoirs Once the feces dries, organisms can become airborne as droplets
• Cage cleaning may pose an infx risk
• Dx by serology (CF vs MIF tests)
• culturing is highly infx and discouraged
• Tx: tetracyclines (preferred), 7-10 days is thought to be sufficient for tx
• Community-acquired PNA (САР).
• Rigors (shaking)
• Can affect multiple organ systems: CNS- meningoencephalitis, Cardiac- myocarditis, Renal- acute renal failure

Salmonella

• Organism: Genus Salmonella
• Salmonella consists of 2 species
• Salmonella enterica and Salmonella bongori
• It is a motile, gram-negative bacillus
• It grows under aerobic and anaerobic conditions
• Location: Ubiquitous bacteria
• Can survive for several weeks in a dry environment and months in water
• Vector/Host: Salmonella enterica subtype in cattle
• Salmonella enterica subtype Cholerasuis in pigs [2]
• Most serotypes are present in a wide range of hosts [
• Transmission: Foodborne outbreaks involving animal and plant-based agricultural products
• Poultry and eggs are common source
• Can spread transovarially from chickens to intact shell
• Salmonella Animal Contact reptiles and amphibians like snakes, lizards, turtles, iguanas, and frogs Live poultry, cats, dogs, hamsters, mice, rats, and hedgehogs
• Zoonotic transmission from sick pets may occur Animals get Salmonella from their environment, by eating contaminated food, or from their mothers
• Clinical Syndromes: Nontyphoidal Salmonella is a major cause of diarrhea worldwide
• Clinically indistinguishable from gastroenteritis caused by other pathogens Symptoms include diarrhea, nausea, vomiting, fever, and abdominal cramping
• A higher ingested dose of bacteria correlates with the severity of diarrhea, illness duration, and weight loss Complications/Invasive disease
• Stool culture is the definitive diagnosi
• Usually self-limited and antimicrobials only indicated for for severe illness
• Use oral therapy such as Azithromycin and oral or iv Fluoroquinolones
• Prevention measures include clean drinking water, hand washing and cooking food properly
• Incubation: 8-72 hours after exposure

Echinococcus

• Cestodes of the genus Echinococcus
• Four species cause disease in humans,
• E. granulosus and E. multilocularis are commonly found in dogs and other carnivores
• dogs, cats, coyotes, and wolves can be vectors of Intermediate hosts for small rodents
• Transmission
• Carnivores are the definitive hosts and harbor the adults which shed eggs within their feces
• granulosus is distributed worldwide, (rural areas where sheep is raising occurs)
• multilocularis is mostly found in northern, cooler temperature countries
• Surgery is best treatment for liver cysts that are secondarily infected or located in the brain, lungs, or kidney
• PAIR is Percutaneous, Aspiration, Injection of Chemicals, and Re-aspiration has largely replaced surge

Brucella

• Organism: Brucella is Small, non-motile, facultative intracellular aerobic rods and stains single, tiny, gram-negative coccobacilli
• Location: Very prevalent in Mediterranean basin
• Vector/Host: Cattle, goat, pigs, etc
• Transmission: Most common through unpasturized milk and cheese
• Person-to-person transmission is extremely rare (tissue transplants)
• The most common zoonotic disease in the world
• The most successful prevention is animal vaccination
• Varies, usually 5-60 days or 1-2 months common
• Treatment with Doxycycline is bacteriostatic, so relapse disease can occur after successful treatment.
• 1986 WHO guidelines recommend Doxycycline (6 weeks) + streptomycin (2-3 weeks) or rifampin (6 weeks

Neurocysticercosis – Neuro.

• Taenia solium (pork tapeworm) cause the cestode parasite
• Life cycle is divided into adult (intestinal tapeworm) and larval (metacestode)
• Endemic in all areas of the world where pigs are raised
• Vector or host:Intermediate host is pig and Humans are the obligate host
• Humans become infected by ingesting undercooked pork infected with T. solium cysticerci Pigs ingest the proglottids or ova from human fecal material
• Typically follows ingestion of ova from a tapeworm carrier
• Clinical presentation depends on the location and number of cysticerci [
• Parenchymal: Usually presents with seizures
• Extraparenchymal involves the subarachnoid space, ventricles, spinal cord, or the eye and can be complicated by increased ICP and hydrocephalus
• Neuroimaging or CT (to detect) may show the scolex at times [
• Prevention is improved sanitation + porcine pig vaccine Porcine vaccine for pigs is recommended and screening and the treatment of carriers recommended

Q Fever

• Organism: Coxiella burnetii (bacterium that is 0.3 to 0.7 µm long and, unlike rickettsiae, enters the cell via a passive mechanism

• It survives within the phagolysosome of host cells such as macrophages The spore stage allows Coxiella to withstand harsh environmental conditions

• It exhibits antigenic variation known as "phase variation"

• Distributed worldwide, except for Antarctica and New Zealand [

• Vector/Host: Goats, sheep, and cattle are reservoir

• Other reservoir species include cats, rabbits, birds, and ticks

• Humans are usually infected by inhalation of the organism from contaminated farm

• 1-10 inhaled organisms are needed to cause infection

• Can manifest as a self-limited febrile illness (2-14 days) or complications Serology is used to diagnose Q fever Coxiella undergoes LPS antigenic variation with Acute Q fever is diagnosed if the anti-phase II is acute

• Treatment involves doxycycline for 2 weeks

Leishmaniasis

• Organism: Leishmaniasis is caused by multiple species (over 20) of Leishmania parasites

• Leishmaniasis is found in every continent except Antarctica and Australia

• Vector (Host): Transmitted by the bite of sandflies and can be maintained with and infected animals

• Sandflies inoculate flagellated forms of the parasite (promastigotes) into the skin

• 2 major forms: Visceral Leishmaniasis (VL) and Cutaneous Leishmaniasis (CL)

• A third form, and Mucocutaneous Leishmaniasis can also occur

• Definitive diagnosis includes demonstration of the parasite in a clinical specimen by histology, culture, or PCR

• Specimens should be collected from lesions without evidence of secondary infection

• Treatment may include accelerated healing and reduced recurrence

• Prevention: Focus on barrier method

Concise study notes on the rabies virus, covering its prevalence, transmission, and clinical symptoms. These notes include diagnostic methods such as fluorescent antibody testing and histopathology to reveal Negri bodies.