Nivalenol as well as deoxynivalenol and T-2 toxin have been used as biological warfare agents in Laos and Cambodia as well as in Afghanistan. The Soviet Union has been alleged to have provided the mycotoxins and to have used them themselves in Afghanistan. All three compounds could be identified in the vegetation at affected sites, whereas T-2 toxin could also be found in urine and blood samples of victims.[7]
The best documented use of trichothecenes in warfare is the yellow rain controversy, this describes a number of attacks in Southeastern Asia as well as Laos and Afghanistan, which used a “yellow rain” as described by witnesses. The toxins were delivered as what has been described as a cloud of yellow dust or droplets. An article by L. R. Ember published in 1984 in Chemical Engineering News describes the use of trichothecenemycotoxins as biological weapons in Southeast Asia in a very detailed manner.[8] In it reports of survivors and eyewitnesses as well as prisoners of war and soviet informants can be found together with information on the presence of soviet technicians and laboratories. This led to the conclusion that these toxins have been used in Southeast Asia and Afghanistan. The Russian government however refuses to give a statement on these pieces of evidence. Furthermore, it has been shown that samples taken on the location of attacks contain these toxins, while sites that have not been attacked do not show any signs of toxins in them.
Even though it remains questionable if all witness reports are reliable sources of evidence, the symptoms recorded are typical for intoxication with trichothecenes.
There was a number of ways in which trichothecenes were weaponized, such as dispersion as aerosol, smoke, droplets or dust from aircraft, missiles, handheld devices or artillery.[9]
As nivalenol is a mycotoxic product of certain Fusarium species it is often found in infected wheat and grain. As unprocessed wheat and grain product are often used as feed for livestock animals these are at a higher risk of nivalenol intake.
Toxicity studies in swine that received a dose of 0.05 mg nivalenol/kg body weight twice daily showed no lethal effects. Most nivalenol was secreted with the feces and did not reach the bloodstream despite the fact that there was still nivalenol upstage over the intestines after 16 hours of feeding. There were further no nivalenol metabolites found in feces or urine within the first three days.[18] After a week of exposure to 2.5 or 5 mg nivalenol kg bw twice a day a microbiological adaptation was seen as nivalenol metabolites (de-epoxidated nivalenol) could be found in feces and urine.
In rats and mice nivalenol showed to be toxic with adverse effects of growth retardation and leukopenia already noticed at lowest doses of 0.7 mg/kg bw per day. Lethal doses were dependent on the route of administration/intake of nivalenol. As nivalenol is normally taken up with feed the LD50 of oral administration which is 38.9 mg/kg bw per day in mice and 19.5 mg/kg bw per day in rats can be used as standard. The LD50 of intravenous, intraperitoneal and subcutaneous (SC) is between 7 and 7.5 mg/kg bw per day.[19]
毒性の詳細
The toxicity of nivalenol in humans is for the most parts unknown yet, but it was investigated in mice, rats and hamster cells. Thereby the toxicity was divided in the following topics: acute/subacute, subchronic, chronic and carcinogenicity, genotoxicity, developmental toxicity studies and studies on reproduction, immunotoxicity/hematotoxycity and effects on nervous system.
Acute/subacute toxicity
The oral LD50 of nivalenol was found to be 38.9 mg/kg bw in mice whereas the intraperitonal, subcutaneous and intravenous routes of exposure gave LD50 values of 5–10 mg/kg bw. In mice already within 3 days the most deaths occurred after oral exposure through marked congestion and haemorrhage in intestine, in acute toxicity also lymphoid organs are included. Nivalenol given over time periods of 24 days in lower doses (ca. 3,5 mg/kg bw) showed significant erythropenia and slight leukopenia.[19]
Subchronic toxicity
The subchronic toxicity was tested by feeding mice with a daily dose of 0 to 3.5 mg nivalenol/ kg bw for 4 or 12 weeks. The observations after 4 weeks were reduced body weight and food consumption. The reduction in body weight can be explained by statistical decrease in organ weight in thymus, spleen and kidneys. Whereas the consumption time was less for female mice in comparison to male mice. After 12 weeks the toxin consumption resulted in reduction of relative organ weight in both males and females. Hereby only the liver was affected and no histopathological changes were observed.[19]
Chronic toxicity and carcinogenicity
Female mice were fed with different doses of nivalenol (0, 0.7, 1.4 or 3.5 mg nivalenol /kg bw) for one or two years to investigate whether nivalenol is chronic toxic and/or carcinogenic. Also during this study a decrease in body weight and feed consumption was observed. The absolute weight of both liver and kidney was decreased through the two highest doses. The mice fed for one year with nivalenol (also with the lower doses) were affected with severe leukopenia whereas the mice fed for two years had no differences in count of white blood cells. Also "no histopathological changes including tumours were found in liver, thymus, spleen, kidneys, stomach, adrenal glands, pituitary glands, ovaries, bone marrow, lymph node, brain and small intestines with or without Peyer's patch".[19] The lowest doses (0.7 mg nivalenol /kg bw) inhibited the growth and caused leukopenia. "A no observable adverse effect level (NOAEL) could not be derived from these studies. IARC (1993) concluded that there is inadequate evidence of carcinogenicity of nivalenol in experimental animals. No human data were available. The overall conclusion was that the carcinogenicity was not classifiable (group 3)".[19]
Genotoxicity
It was found that nivalenol effects the genes of Chinese hamster V79 (CHO) cells by slightly increased frequencies of chromosomal aberrations and sister chromatid exchange. The DNA was damaged in CHO cells as well as in mice. In mice (given 20 mg nivalenol /kg bw orally or 3.7 mg /kg bw ip) the DNA of kidney, bone marrow, stomach, jejunum and colon was damaged. The DNA of the thymus and liver was not effected. In organs with DNA damage no necrotic changes were found upon histopathological examination. It can be concluded that an adequate evaluation of the genotoxicity is not allowed based on the available data.[19]
Developmental toxicity and studies on reproduction
For developmental and reproduction studies pregnant mice were injected with different amounts of purified nivalenol on days 7–15 of gestation and for one additional study with mouldy rice containing nivalenol. The studies showed that the toxin is embryotoxic in mice. No evidence of teratogenicity was given. "The LOAEL in reproduction studies with nivalenol given by oral exposure was stated to be 1.4 mg/kg bw given in the feed throughout gestation and 5 mg/kg bw when given by gavage on days 7–15".[19] Data from other species and on reproductive effects in adult males and females are not provided yet.[19]
Immunotoxicity/haematotoxicity
Acute toxicity of nivalenol induces bone marrow toxicity and toxicity of lymphoid organs. Long-term exposure may result in erythropenia and/or leukopenia. In mice it was also observed that nivalenol increased the presence of serum IgA, "accompanied by immunopathological changes in kidneys analogous to human IgA-nephropathy".[19] The blastogenesis in cultured human lymphocytes, proliferation of human male and female lymphocytes stimulated with phytoheamagglutin and pokeweed and immunoglobulin production induced by pokeweed, are inhibited by nivalenol. The effects of nivalenol are in the same range as same doses of deoxynivalenol, whereas the T-2 toxin are 100 fold more toxic. An additive effect is gained by combination of nivalenol with T-2 toxin, 4,15-diacetoxyscirpenol or deoxynivalenol.[19]
Effects on nervous system
About the nervous system no data has been provided yet.[19]
^ abc“Scientific Opinion on risks for animal and public health related to the presence of nivalenol in food and feed”. European Food Safety Authority (EFSA) Journal11 (6): 1-5. (2013).
^ abcHedman, R.; Pettersson, H.; Lindberg, J.E. (2009). “Absorption and metabolism of nivalenol in pigs”. Archiv fur Tierernaehrung50-1 (1): 13-24. doi:10.1080/17450399709386115. PMID9205733.
^Gupta, R. C., ed (2015). Handbook of Toxicology of Chemical Warfare Agents. Academic Press. pp. 353-369. ISBN9780128001592
^Venkataramana, M.; Chandranayaka, S.; Prakash, H. S.; Niranja, R. (2014). “na, S. (2014). Mycotoxins Relevant to Biowarfare and Their Detection”. Biological Toxins and Bioterrorism: 22. doi:10.1007/978-94-007-6645-7_32-1.
^ abcdSidell, F. R.; Takafuji, E. T.; Franz, D. R. (1997). Medical Aspects of Chemical and Biological Warfare. United States Government Printing. pp. 662-664. ISBN978-9997320919
^Sugita-Konishi, Y.; Pestka, J. J. (2001). “Differential upregulation of TNF-alpha, IL-6, and IL-8 production by deoxynivalenol (vomitoxin) and other 8-ketotrichothecenes in a human macrophage model.”. Toxicol Environ Health A64 (8): 619-636. doi:10.1080/152873901753246223. PMID11766169.
^Sundstøl Eriksen, G.; Pettersson, H.; Lundh, T. (2004). “Comparative cytotoxicity of deoxynivalenol, nivalenol, their acetylated derivatives and de-epoxy metabolites”. Food and Chemical Toxicology42 (4): 619-624. doi:10.1016/j.fct.2003.11.006. PMID15019186.
^Pettersson, H.; Hedman, R. (1997). “Toxicity and metabolism of nivalenol in farm animals”. Cereal Research Communications (Akadémiai Kiadó) 25-3 (3): 423-427. doi:10.1007/BF03543746.
