Japanese medaka Oryzias latipes were cultured at the U.S. Army Biomedical Research and Development Laboratory for use as aquatic toxicity test animals. During routine histological examination, granulomatous lesions were detected, and a low prevalence of Mycobacterium sp. was suspected in the culture system. Fish maintained under experimental and breeding conditions were cultured for acid-fast bacteria. Modified Middlebrook 7H 10 medium with albumin, dextrose, and catalase (ADC) enrichment was used to recover mycobacteria from whole-fish homogenates via three isolation procedures. Highest isolation rates were obtained by submerging whole fish in individual bags of modified broth at a 1:10 (weight : Volume) dilution for 1 h, then homogenizing the whole fish and plating diluted samples on solid medium using a plate count method. Medaka, ranging in age from 2 to 27 months, were positive for Mycobacterium abscessus with prevalences of 25%–100%. Mean bacterial counts for all groups examined ranged from 6.7 × 102 to 4.5 × 108 colony-forming units per gram of fish. Throughout the study, fish remained apparently healthy, exhibited no clinical signs of piscine mycobacteriosis, and suffered no significant mortality.
Journal Article Transmission of Venezuelan Equine Encephalomyelitis Virus by Aedes sollicitans and Aedes taeniorhynchus (Diptera: Culicidae) Get access Michael J. Turell, Michael J. Turell Virology Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland 21702-5011 Search for other works by this author on: Oxford Academic PubMed Google Scholar George V. Ludwig, George V. Ludwig Virology Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland 21702-5011 Search for other works by this author on: Oxford Academic PubMed Google Scholar Joseph R. Beaman Joseph R. Beaman Virology Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland 21702-5011 Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Medical Entomology, Volume 29, Issue 1, 1 January 1992, Pages 62–65, https://doi.org/10.1093/jmedent/29.1.62 Published: 01 January 1992 Article history Received: 24 April 1991 Accepted: 12 August 1991 Published: 01 January 1992
MD 21701-50110 The recent introduction of Aedes L!bopictus maintained at 26°C, and apples or a 5' sucrose(Skuse) into the Americas has led to concern solution were provided as a carbohydrate0 that this mosquito might serve as a vector of source. The mosquitoes were allowed to ovipositCN both native as well as exotic viruses. (Bartnett 3 days later, and mosquitoes were assayed for1986, Shroyer 1986, Sprenger and Wuithirany- viral infection and transmission ability begin-agool 1986). Experimental and field data, re- ning 7 days after the infectious bloodmeal. Dur-cently reviewed by Shroyer (1986), indicate that ing each transmission trial, mosquitoes were al-this species is capable of transmitting chikun- lowed to feed either individually, or in groupsgunya, Japanese encephalitis, yellow fever, of up to 5 mosquitoes each on anesthetizedWest Nile, Ross River, and all 4 serotypes of hamsters.dengue viruses, as well as St. Louis encephalitis After the feeding period, the mosquitoes wereand western equine encephalitis viruses, cold-anesthetized and their legs and bodies tri-We evaluated the potential of the F genera- turated separately in I ml of diluent (10( fetaltion of a Houston, Texas strain of Ae. albopic- bovine serum in Medium 199 with Hanks' saltstus to transmit Rift Valley fever (RVF) virus, and antibiotics). Mosquito or leg suspensionsThis strain of Ae. albopictus was provided by were frozen at -70'C until they were tested forDr. C. Mitchell and is the same strain used in virus by a standard plaque assay on Vero cellsother vector competence studies (Mitchell et al. (Gargan et al. 1983). Recovery of virus from the1987). The ZH501 strain of RVF virus, isolated body, but not the legs, indicated that viral in-from a human case during the outbreak in fection was limited to the midgut and had notEgypt in 1977 (Meegan 1979) and passed twice disseminated to the hemocoel, while recovery ofin fetal rhesus lung cells, was used throughout virus from both legs and body indicated thatthese studies. the mosquito had a disseminated infection.Female mosquitoes, 5 to 10 days old reared at (Turell et al. 1984). Hamster death was used as261C with a 16:8 L:D photoperiod, were al- the criterion for virus transmission, because in-lowed to feed on an anesthetized hamster that fection with RVF virus is virtually 100'( fatalhad been inoculated with RVF virus 24 hours for hamsters (Gargan et al. 1983). All hamsterspreviously. Immediately after the infectious surviving 21 days after being fed on by a mos-bloodmeal, a sample of the engorged mosqui- quito with a disseminated infection were chal-toes was titrated to determine the titer of virus lenged with 10' plaque-forming units (PFU) ofin the blood they had ingested. The remaining the ZH501 stock virus to demonstrate their sus-engorged mosquitoes were placed in a 3.8 liter ceptibility to RVF viral infection. Ten percentcardboard container with netting over one end. liver suspensions were prepared from a sampleThis container was placed in an incubator of the hamsters that died after exposure to mos-
Abstract This study describes the use of a panel of immune assays, originally developed by the National Toxicology Program for assessing xenobiotic-induced immunotoxicity in mice, to quantify the effects of sublethal malathion exposure on the immune responses of fish. For this study, Japanese medaka (Oryzias latipes) were exposed subchronically to the organophosphate pesticide malathion in a series of two experiments. In the first set of studies, fish were exposed for 7 or 14 d to untreated well water (i.e., controls) or to waterborne malathion at 0.2 or 0.8 mg/L. Following exposure, fish from each group were sacrificed and their kidneys (primary organ of leukopoiesis in fish and equivalent to mammalian bone marrow) were used to provide cells for assessing any malathion-induced effects upon nonspecific and acquired immune defense mechanisms. Effects upon humoral-mediated immunity were determined by enumerating antibody plaque-forming cell (PFC) numbers from a subset of fish exposed to malathion for 14 d and then injected intraperitoneally (ip) with sheep erythrocytes (sRBC). Results of these studies demonstrated that while malathion exposure had no significant effect upon hematocrit/leukocrit values or upon mitogen-stimulated T-cell lymphoproliferation, PFC numbers in the kidney of exposed fish were significantly reduced (compared to control fish) in a dose-dependent manner. In addition, total recoverable kidney cell numbers and viability, as well as superoxide anion production by kidney phagocytes, were reduced slightly (compared to control values) in fish exposed for 14 d to the highest malathion concentration tested. In the second set of experiments, medaka exposed for up to 21 d to either 0.1 or 0.3 mg malathion/L were challenged ip with an LD50 dose of the bacterial fish pathogen Yersinia ruckeri. Results from these infectivity studies demonstrated that exposure to either malathion concentration for 14 or 21 d reduced host resistance against Yersinia infection. Taken together, these findings demonstrate the applicability of mammalian immune assays for predicting malathion-induced immunosuppression in a teleost fish, as well as the potential utility of a small laboratory fish to serve as an alternate model for mammals in immunotoxicological studies.
Abstract Composting is being explored as a means to remediate 2,4,6-trinitrotoluene (TNT) contaminated soils. This process appears to modify TNT and to bind it to organic matter. The health hazards associated with dusts generated from such materials cannot be predicted without knowing if the association between TNT residues and compost particulate is stable in biological systems. To address this question, single doses of [l4C]-TNT, soil spiked with [14C]-TNT, or compost generated with [l4C]-TNT-spiked soils were administered to rats by intratracheal instillation. The appearance of 14C in urine and tissues was taken as an indication of the bioavailability of TNT residues from compost particles. In rats instilled with neat [14C]-TNT, about 35% of the UC dose appeared in urine within 3 d. The l4C excreted in urine by these rats decreased rapidly thereafter, and was undetectable by 4 wk after treatment. Similar results were obtained with soil-treated rats. In contrast, after treatment with [14C]-TNT-labeled compost, only 2.3% of the total 14C dose appeared in urine during the first 3 d. Low levels of 14C continued to be excreted in urine from compost-treated rats for more than 6 mo, and the total amount of HC in urine was comparable to that in TNT-treated animals. Determination of the radiolabel in tissues showed that MC accumulated in the kidneys of rats treated with labeled compost but not in rats treated with [l4C]-TNT or [14C]-TNT-spiked soil. These results indicate that the association between TNT and particulate matter in compost is not stable when introduced into the lungs. Accumulation of 14C in kidneys suggests the presence of a unique TNT residue in compost-treated rats. The rate of excretion and tissue disposition of UC in rats treated with TNT-spiked soil indicate that TNT in soil is freely available in the lungs.
Imunocompetence is usually monitored using a tiered approach that is based upon several parameters including immunopathology, immune function, and host resistance. Through the efforts of numerous investigations, well-characterized immune assays validated in rodents for their sensitivity and reproducibility in assessing xenobiotic-induced immunotoxicity are currently available. Recently, many of these same endpoints have been utilized in non-mammalian species as indicators to predict chemical-induced immunotoxicity. In this laboratory, immune assays that measure immunopathology, antibody-forming cell response to T-dependent antigens, lymphocyte proliferation, macrophage function, antioxidant activity, and host resistance against infectious bacteria have been employed successfully to assess metal-, pesticide-, aromatic hydrocarbon-, and mixture-induced immunotoxicity in laboratory-reared Japanese medaka (Oryzias latipes). These same assays have also proven successful in feral fish populations for predicting risk(s) associated with habitation in contaminated aquatic environments. For example, smallmouth bass (Micropterus dolomieu) collected from a polychlorinated biphenyl-contaminated site had reduced phagocyte function, oxyradical production, and antioxidant levels (compared to reference fish), while circulating leukocyte profiles and lymphocyte proliferation by splenic T-cells were altered in organochlorine-exposed walleye (Stizostedium vitreum vitreum). Results of the aforementioned studies demonstrate that immune assays developed and validated in a laboratory fish model can be successfully applied to feral fish populations to predict the toxicological hazards associated with exposure to immunomodulating aquatic pollutants.
Experimental studies were undertaken to ascertain the vector potential of North American (Houston and Alsace) and South American (Sao Paulo and Santa Teresa) strains of Aedes albopictus (Skuse) for an epizootic (Trinidad donkey) strain of Venezuelan equine encephalomyelitis (VEE) virus. Infection rates were similar in all four strains of Ae. albopictus tested after ingestion of VEE virus from a viremic hamster. Virus disseminated from the midgut to the hemocoel in about 80% of infected mosquitoes, regardless of the dose ingested (10(4.6) to 10(5.7) plaque-forming units per mosquito) or the time of extrinsic incubation (7-35 d). Although all four strains of this mosquito transmitted VEE virus by bite to hamsters, transmission rates were significantly higher for the South American strains (24%, 40 of 170) than for the North American strains (5%, 9 of 165). Although VEE virus has never been isolated from Ae. albopictus, the introduction of this species into the Americas may allow it to serve as an amplification vector in areas where epizootic strains of VEE are found or introduced.
It is critical to establish baseline health endpoints in animal models used in toxicological studies. In mammalian models, procedures for monitoring the health status of test animals have been established and in use for many years; in many aquatic models, including medaka, much of this routine health screening has not been documented. Thus, the purpose of this study was to characterize routine health parameters in medaka and to identify parameters sensitive to changes in health status which could affect the suitability of animals for use in general toxicity and immunotoxicological studies. The endpoints assessed included histopathology (31 organs), identification of endogenous bacterial flora and, gross necropsy including body weight, length, hematocrit, leukocrit, and plasma immunoglobulin levels. Additional parameters included anterior kidney (the teleost bone marrow equivalent) weight and cell yields plus superoxide anion production. Histological findings included observation of age-related incidence of granulomatous lesions in a variety of organs. Multiple strains of Aeromonas and Pseudomonas were the predominant internal flora in healthy medaka. Hematocrit, leukocrit and plasma IgM levels were within the normal range for this species. Comparisons were made between healthy and handling-stressed fish. Evaluation of data collected to date suggest that leukocrit and superoxide anion production were themore » most sensitive indicators of the fish health status and suitability for use in general and/or immunotoxicological studies.« less
Abstract : The recent introduction of Aedes albopictus into the Americas has led to concern that this mosquito might serve as a vector of both native as well as exotic viruses. Experimental and field data indicate that this species is capable of transmitting chikungunya, Japanese encephalitis, yellow fever, West Nile, Ross River, and all 4 serotypes of dengue viruses, as well as St. Louis encephalitis and western equine encephalitis viruses. We evaluated the potential of the F3 generation of a Houston, Texas strain of Ae. albopictus to transmit Rift Valley fever (RVF) virus. Female mosquitoes, 5 to 10 days old reared at 26 C with a 16:8 L:D photoperiod, were allowed to feed on an anesthetized hamster that had been inoculated with RVF virus 24 hours previously. Recovery of virus from the body, but not the legs, indicated that viral infection was limited to the midgut and had not disseminated to the hemocoel, while recovery of virus from both legs and body indicated that the mosquito had a disseminated infection. Ae. albopictus should be considered a potential vector of RVR virus, should it be introduced into the southern United States. Reprints.
