Venezuelan Equine Encephalitis
Venezuelan Equine Encephalitis
PATHOGEN SAFETY DATA SHEET – INFECTIOUS SUBSTANCES
SECTION I – INFECTIOUS AGENT
NAME: Venezuelan equine encephalitis virus
SYNONYM OR CROSS REFERENCE: Venezuelan equine encephalomyelitis, VEEV, VEE, Venezuelan equine fever, arbovirus
CHARACTERISTICS: This spherical arbovirus belongs to the Togaviridae family and is an alphavirus (1). It is 70 nm in diameter and has an enveloped single stranded RNA genome (2, 3). There are six subtypes of VEE viruses, although only varieties AB and C of subtype 1 are epizootic, while the other subtypes and varieties are enzootic (3).
SECTION II – HAZARD IDENTIFICATION
PATHOGENICITY/TOXICITY: In humans, this virus usually causes mild to severe influenza-like symptoms, however 4-14% of cases develop neurological complications (2). Children and young adults are more likely to develop encephalitis caused as a result of infection; however, fatalities in humans are rare at about 1% of all reported cases (4). Usually, flu-like symptoms such as headache, myalgia, fatigue, vomiting, nausea, diarrhoea, pharyngitis and fever appear abruptly, 2 to 5 days after exposure to the virus (3). The VEE virus can also cause retro-orbital and occipital headaches as well as leucopenia and tachycardia (3). Symptoms of encephalitis, only appearing in a minority of cases, occur 4-10 days after exposure and include somnolence, convulsions, confusion, photophobia, and coma. Lethal human cases are usually caused by encephalitis as well as brain, lung and gastrointestinal bleeding (3). Long-term neurological damage can be caused by this virus and it can infect the foetus in pregnant women causing birth defects and stillbirths (4). Generally, the symptoms last between 3 and 8 days and can be biphasic, recurring 4 to 8 days after the initial symptoms (5).
EPIDEMIOLOGY: The epizootic and enzootic strains of the VEE virus range from northern Argentina to Florida and parts of the Rocky Mountains; however, it is most prevalent in northern South America (3, 4). The virus was first observed in horses in 1935 after outbreaks in Columbia, Venezuela and Trinidad, and was isolated in 1938 (3, 6). In the 1960’s, over 200,000 human cases and 100,000 equine deaths were reported in Colombia and smaller epidemics occurred in Venezuela and Mexico (3). Between 75,000 and 100,000 infections were reported in Venezuela and Colombia in 1995 (3). The outbreaks usually occur after a season of heavy rains, due to increases in the mosquito population (3, 7). Vaccinations of equines with the TC-83 vaccine and protection against mosquitoes (protective clothing, insecticides) are some of the proposed ways to reduce VEE outbreaks (3).
HOST RANGE: Horses and humans are the most common hosts; however, a variety of other animals have been shown to be susceptible to infection (8) . These include mammals such as cats, dogs, cattle, goats, pigs, rodents, and birds (8).
INFECTIOUS DOSE: 1 viral infectious particle injected subcutaneously is enough to infect an individual with the VEE virus (9).
MODE OF TRANSMISSION: The VEE virus is most often transmitted by infected mosquito bites, although, it is also very contagious through aerosols (6, 8). Subcutaneous injection, nasal instillation, and contact with broken skin or contaminated animal bedding are other ways to spread the virus, particularly in a laboratory setting (5).
INCUBATION PERIOD: The incubation period is usually about 2 to 6 days after exposure to the virus, but can be as short as 24 hours (8, 10).
COMMUNICABILITY: Instances of person-to-person transmission have not been reported for the VEE virus, although an infected individual can transmit the virus to mosquitoes (8). Generally, humans and equines become infected by mosquitoes of the Psorophora and Ochlerotatus genuses. Equines can spread the virus to each other through aerosols and to mosquitoes via bites (11).
SECTION III – DISSEMINATION
RESERVOIR: There are two types of cycles involved in the VEE virus (1). The enzootic cycle is maintained by rodents and mosquitoes (11). The epizootic cycle implicates horses, mosquitoes and humans, although there is the potential for the virus to affect many other animal species (11). Horses are the amplifying host in the cycle and are necessary for a larger outbreak of VEE (4).
ZOONOSIS: Capable of zoonosis. This virus is spread between horses and humans via mosquitoes (11).
VECTORS: The VEE virus is typically spread by mosquitoes, although certain types of ticks and mites can spread the virus as well (3). The Culex (Melanoconion) mosquito is normally responsible for the dispersal of the enzootic strain of the VEE virus (3, 6). Ochlerotatus taeniorhynchus, Psorophora confinnis, Psorophora columbiae, Ochleratus sollicitans, Mansonia titillans and Anophilis aquasalis are some of the species of mosquitoes known to carry the epizootic varieties of the VEE virus (3, 5, 7).
SECTION IV – STABILITY AND VIABILITY
DRUG SUSCEPTIBILITY: No drug susceptibilities have been determined to date (5).
SUSCEPTIBILITY TO DISINFECTANTS: Like other enveloped viruses, the VEE virus is susceptible to disinfectants such as 1% sodium hypochlorite, 4% formaldehyde, 2% gluteraldehyde, 70% ethanol, 3-6% hydrogen peroxide, 2% and peracetic acid (9).
PHYSICAL INACTIVATION: Microbial inactivation is possible using moist or dry heat (12). Togaviruses can be inactivated by 15 minutes of heat at 65 ºC (13).
SURVIVAL OUTSIDE HOST: The virus is stable in blood and exudates as well as in freeze dried materials (aerosols) (9, 14).
SECTION V – FIRST AID / MEDICAL
SURVEILLANCE: Monitor for symptoms. Confirm infection by isolating the virus from CSF of infected individuals with CNS complications and determine the antibody titre by serology tests such as SN, CF, and HI tests (5, 15, 16). A number of laboratory techniques are available for confirmation of arbovirus infections, including PCR, ELISA and serology as well as immunohistochemical (IHC) staining of tissue sections (15).
Note: All diagnostic methods are not necessarily available in all countries.
FIRST AID/TREATMENT: No specific treatment available. Supportive treatment may be given to alleviate symptoms (8).
IMMUNIZATION: The investigational formalin inactivated TC-83 vaccine is available and recommended for lab workers. This vaccine is quite effective in preventing infection by the epizootic strains of the VEE virus (7, 14). While the TC-83 vaccine is used in labs, there is no licensed vaccine available for the general population (3).
PROPHYLAXIS: None apart from avoidance of mosquito bites.
SECTION VI – LABORATORY HAZARDS
LABORATORY-ACQUIRED INFECTIONS: Several laboratory-acquired cases of the VEE virus have been reported. As of 2006, a total of 186 cases and 2 deaths were documented (16). Most of these incidents were related to egg culture techniques, suckling mice and aerosol exposure (9). A physical exam and a careful medical check-up are recommended after a laboratory accident involving VEE in order to avoid laboratory-acquired infections (16).
SOURCES/SPECIMENS: Arboviruses may be present in blood, cerebrospinal fluid, urine and exudates (14). The virus may be found in nasal, eye and mouth secretions of infected animals as well as in contaminated animal bedding (5, 14).
PRIMARY HAZARDS: The greatest risks when working with the VEE virus are exposure to infected aerosols, accidental subcutaneous inoculation, and contact with broken skin or contaminated animal bedding (14).
SPECIAL HAZARDS: The VEE virus is fairly stable in dried blood and exudates (14).
SECTION VII – EXPOSURE CONTROLS / PERSONAL PROTECTION
RISK GROUP CLASSIFICATION: Risk group 3 (17).
CONTAINMENT REQUIREMENTS: Containment Level 3 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures.
PROTECTIVE CLOTHING: Personnel entering the laboratory should remove street clothing and jewellery, and change into dedicated laboratory clothing and shoes, or don full coverage protective clothing (i.e., completely covering all street clothing). Additional protection may be worn over laboratory clothing when infectious materials are directly handled, such as solid-front gowns with tight fitting wrists, gloves, and respiratory protection. Eye protection must be used where there is a known or potential risk of exposure to splashes (18).
OTHER PRECAUTIONS: All activities with infectious material should be conducted in a biological safety cabinet (BSC) or other appropriate primary containment device in combination with personal protective equipment. Centrifugation of infected materials must be carried out in closed containers placed in sealed safety cups, or in rotors that are loaded or unloaded in a biological safety cabinet. The use of needles, syringes, and other sharp objects should be strictly limited. Open wounds, cuts, scratches, and grazes should be covered with waterproof dressings. Additional precautions should be considered with work involving animals or large scale activities (18).
SECTION VIII – HANDLING AND STORAGE
SPILLS: Allow aerosols to settle and while wearing protective clothing, gently cover spill with paper towels and apply appropriate disinfectants, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up (18).
DISPOSAL: Decontaminate all material used before disposal via incineration, and steam sterilization (18).
STORAGE: Store in sealed containers that are appropriately labelled inside the locked containment level 3 laboratory (18).
SECTION IX – REGULATORY AND OTHER INFORMATION
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: July 2010.
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Trichomonas vaginalis
PATHOGEN SAFETY DATA SHEET – INFECTIOUS SUBSTANCES
SECTION I – INFECTIOUS AGENT
NAME: Trichomonas vaginalis
SYNONYM OR CROSS REFERENCE: Trichomoniasis, vaginitis.
CHARACTERISTICS: Trichomonas vaginalis is a parasitic protozoan flagellate, and organisms vary in size but are usually around 10 μm in length and 7 μm in width(1,2). It usually has an oval or pear-like shape, but can assume an amoeboid form when attached to vaginal epithelial cells. T. vaginalis has a total of 5 flagella, four of which are located at its anterior portion. The fifth flagellum is incorporated within the undulating membrane(1,3). The anaerobic parasite can only exist as a trophozoite and lacks a cystic stage, reproducing by longitudinal binary fission. Growth is optimized at 37°C at pH 6.0 – 6.3, but can survive at up to pH 7(4).
SECTION II – HAZARD IDENTIFICATION
PATHOGENICITY/TOXICITY: T. vaginalis is generally restricted to the genitourinary tract by the host’s immune system, and is the etiological agent of human trichomoniasis(2). Infection has been associated with an increased risk of human immunodeficiency syndrome in both sexes(4).
In women: Symptoms of infection include vaginal secretion that is scanty and mixed with mucus; malodorous discharge that is frothy, yellow or green, mycopurulent, and copious(4). The protozoan can be found in the vagina, cervix, bladder, Bartholin’s, Skene’s, and periurethral glands. Complications may result in cervical erosion, cervical cancer, infertility, adnexitis, pyosalpinx, and endometritis. Premature rupture of the placental membranes can occur in pregnant women, resulting in premature birth and low-birth weight(5). Acute infections are characterised by severe pruritus, vaginitis, vulvitis with dysuria and dyspareunia, and hemorrhagic spots on the mucosa (in 2% of patients) which results in colpitis macularis or petechiae (strawberry cervix). In females, 50% of cases are asymptomatic. Infection can persist for long periods of time in the urogenital tract of women. 25 – 50% are asymptomatic for the first 6 months of infection, and organisms can survive indefinitely in the lower urogenital tract if left untreated(1,6).
In men: Prevalence is lower in men, and infection is often asymptomatic(7). Infection in men can be present in the prostate, seminal vesicles, and epididymis. Complications are rare, but can potentially lead to genitourinary inflammation disease, sterility, scanty, clear to mucopurulent discharge, dysuria, non-gonococcal urethritis, prostatitis, balanoposthitis, epididymitis, and urethral disease(4). Infection is usually mild with no symptoms, thus making men potential carriers. Spontaneous resolution of infection is common as the oxidative nature of the male genital tract is speculated to be inhibitory to pathogenic factors of infection, which usually remains for 10 days or less(1).
EPIDEMIOLOGY: Worldwide – trichomoniasis caused by T. vaginalis is one of the most common non-viral sexually transmitted diseases with an estimated 170 million cases occurring annually (no seasonal variability)(1), and incidence has been found to be high in non-hispanic black women(5). Infection usually occurs in women during reproductive years, and occurrence before menarche or after menopause is rare(4). Fourteen to 60% of male infections are associated with known infected female partners(1).
HOST RANGE: Humans(1).
INFECTIOUS DOSE: Experimental studies have shown that urogenital inoculation with 10,000 to 120,000 organisms has resulted in transmission, although epidemiological examinations have shown that the infective dose in women is low and the infection rate is high(8-10).
MODE OF TRANSMISSION: Commonly spread through sexual contact with vaginal or urethral discharges of infected persons(1), and transmission of organisms via artificial insemination of infected cryobanked semen is also possible(11). Non-sexual transmission is rare but has been observed in cases involving contaminated douche nozzles, moist wash-clothes, specula, or toilet seats(1,12,13). Transmission to newborn infants from infected mothers is possible and is observed in 2 – 17% of cases, and can result in urinary tract or vaginal infections(1).
INCUBATION PERIOD: Ranges from 3 – 28 days with an average of 7 days(4,14).
COMMUNICABILITY: Infection can persist for a significant period of time in asymptomatic cases(14), from months to years. SECTION III – DISSEMINATION
RESERVOIR: Humans, typically females, while men may act as a reservoir for infection(4).
ZOONOSIS: None.
VECTORS: None.
SECTION IV – STABILITY AND VIABILITY
DRUG SUSCEPTIBILITY: The only drugs that have been approved by the FDA for use in the United States are metronidazole (although the use of this drug can increase the incidence of preterm birth)(15), and Tinidazole (trade name known as Tindamax)(16). Ornidazole, secnidazole, and nimorazole can be used in countries outside of the US. In vitro testing has shown that nitroimidazole EU11100 also has similar efficacy as metronidazole(15).
DRUG RESISTANCE: Studies have shown that at least 5% of clinical cases of trichomoniasis are caused by metronidazole-resistant T. vaginalis, and cross-resistance to tinidazole is a concern as the two drugs are similar in modes of action (4).
SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to 1% sodium hypochlorite, and 70% ethanol(17).
PHYSICAL INACTIVATION: Inactivated below pH 5(4). Organisms cannot survive long (several hours) in dry conditions(1).
SURVIVAL OUTSIDE HOST: The organism grows best at 37°C, and specimens in urine should be considered viable for only 30 minutes to avoid false negatives (2 hours if PCR is used)(18). Live T. vaginalis have been found in swimming pool water, in urine, and semen after up to 6 – 24 hours, and up to 30 – 45 minutes when exposed to air(1,19,20). Studies have also shown that T. vaginalis organisms are able to survive through the cryopreservation process of human semen, making infection via artificial insemination possible(11).
SECTION V – FIRST AID / MEDICAL
SURVEILLANCE: Monitor for symptoms. Current laboratory diagnoses include direct microscopic observation, cell culture, immunological techniques, PCR assay, nucleic acid probe test, immunochromatographic capillary-flow dipstick technology, DNA probing and gene amplification, and in situ hybridization(2,9,16).
Note: All diagnostic methods are not necessarily available in all countries.
FIRST AID/TREATMENT: Topical vaginal medications and pessaries (such as clotrimazole, povidone-iodine, nonoxynol-9, and arsenical pessaries) may be prescribed for treatment in women to lessen the effects of symptoms; however, these do not consistently cure disease(4). Topical paromycin has been found to be effective, but side effects can be mild to severe(21). There are no topical medications available for men. Metronidazole can be administered orally or intravenously, with cure rates of 85-95%(1); Metronidazole should not be used by pregnant women in their first trimester as it has been linked to higher prevalence of preterm birth(22).
IMMUNISATION: No vaccinations are currently available. Two vaccines have progressed to the human clinical trials stage in the past 50 years (a heat-killed T. vaginalis vaccine, and SolcoTriovac), although they have not been proven to be effective against T. vaginalis(4).
PROPHYLAXIS: Since many males are asymptomatic and may be carriers, it is important to concurrently treat male partners of infected women to prevent re-infection(4).
SECTION VI – LABORATORY HAZARDS
LABORATORY-ACQUIRED INFECTIONS: None reported to date.
SOURCES/SPECIMENS: Vaginal and urethral secretions, urine, human semen(4,11,18).
PRIMARY HAZARDS: Droplet exposure to mucous membrane, accidental parenteral inoculation and sexual transmission(1,23).
SPECIAL HAZARDS: None.
SECTION VII – EXPOSURE CONTROLS / PERSONAL PROTECTION
RISK GROUP CLASSIFICATION: Risk Group 2(24).
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infected or potentially infected materials, animals, or cultures.
PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes(25).
OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC). The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities(25).
SECTION VIII – HANDLING AND STORAGE
SPILLS: Allow aerosols to settle and, while wearing protective clothing, cover spill with absorbent paper towel. Apply appropriate disinfectant, and starting from perimeter and wipe towards the center. Allow sufficient contact time with the disinfectant before cleaning up.
DISPOSAL: Decontaminate all wastes that contain or have come in contact with the infectious organism before disposing by autoclave, chemical disinfection, gamma irradiation, or incineration(25).
STORAGE: Properly labelled and sealed containers.
SECTION IX – REGULATORY AND OTHER INFORMATION
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: November 2010
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Copyright © Public Health Agency of Canada, 2010 Canada
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