Pulmonary involvement from animal toxins: the cellular mechanisms

Abstract Venomous animals and their venom have always been of human interest because, despite species differences, coevolution has made them capable of targeting key physiological components of our bodies. Respiratory failure from lung injury is one of the serious consequences of envenomation, and the underlying mechanisms are rarely discussed. This review aims to demonstrate how toxins affect the pulmonary system through various biological pathways. Herein, we propose the common underlying cellular mechanisms of toxin-induced lung injury: interference with normal cell function and integrity, disruption of normal vascular function, and provocation of excessive inflammation. Viperid snakebites are the leading cause of envenomation-induced lung injury, followed by other terrestrial venomous animals such as scorpions, spiders, and centipedes. Marine species, particularly jellyfish, can also inflict such injury. Common pulmonary manifestations include pulmonary edema, pulmonary hemorrhage, and exudative infiltration. Severe envenomation can result in acute respiratory distress syndrome. Pulmonary involvement suggests severe envenomation, thus recognizing these mechanisms and manifestations can aid physicians in providing appropriate treatment.

Effects of Bungarus candidus (Malayan krait) venom on general circulation and renal hemodynamics in experimental animals.

Background: Many studies have reported the occurrence of lethal acute renal failure after snakebites. Bungarus candidus (Malayan krait) is a medically important venomous snake distributed widely throughout Southeast Asia. The best known features of systemic envenoming by B. candidus are neurotoxic. Objective: Obtain more information on effects of B. candidus venom on changes in systemic and renal hemodynamics in experimental animals. Methods: Twelve adult male New Zealand white rabbits were used to study the effect of B. candidus venom on general circulation and renal hemodynamics. An anesthetized animal was intravenously injected with B. candidus venom at a dosage of 50μg/kg bodyweight. All changes of parameters were observed after initial post venom injection and recorded at 30 min intervals until 150 minutes after envenomation. Results: After envenomation, cardiovascular responses showed a marked decrease in mean arterial pressure within two minutes, afterwards gradually returning closely to baseline values. There were stepwise decreases in heart rate and cardiac output, while total peripheral resistance was slightly increased. The renal hemodynamics significantly decreased by glomerular filtration rate, effective renal plasma flow and effective renal blood flow, while the filtration fraction significantly increased. Envenomed animals showed a reduction in renal fraction, while renal vascular resistance stepwise increased. The plasma potassium level tended to increase. Animals showed stepwise decreases in urinary excretion of Na+, K+ and Cl-. A marked decrease in plasma calcium level was apparent at 120 minutes, while plasma creatine phosphokinase and lactate dehydrogenase levels increased at 30-120 minutes. Conclusion: A significant drop in blood pressure was attributed to a sustained fall in cardiac output, which would be associated with a reduction in heart rate. Sustained hypotension would contribute to reduction of renal blood flow, which results in decreased GFR.

Moving towards the elimination of rabies in Thailand.

Human rabies is regarded as a fatal disease; however, its occurrence is preventable. Prevention consists of post-exposure prophylaxis (PEP) for humans and controlling the main cause through dog vaccination. In Thailand, health care budgets are increasingly allocated to human PEP rather than eradication of rabies in dogs. This is the case, even if controlling rabies in the dog population is a more cost-effective, longterm approach to prevent human rabies than PEP. While the principal cause of rabies is the roaming stray dogs, the impetus for control and removal is hampered by a lack of awareness of its true impact. The declaration of an annual World Rabies Day, September 8, is an initial effort to raise global awareness of the ongoing and unnecessary tragedy of rabies.

Real-time PCR analysis of dog cerebrospinal fluid and saliva samples for ante-mortem diagnosis of rabies.

The use of a 10-day observation to determine whether a dog is rabid is standard practice. This study was conducted in order to look for evidence of rabies vius in saliva and cerebrospinal fluid (CSF) of suspected live rabid dogs at the time of quarantine by using a SYBR Green real-time RT-PCR based assay for the detection of rabies virus RNA. Saliva and CSF of dogs were collected once on the day of admission for the 10-day quarantine. All test dogs were or became ill and died of rabies within the observation period. Thirteen of 15 dogs (87%) had saliva samples that were positive for rabies RNA. Two dogs with furious rabies had negative saliva samples. Positive CSF samples were found in 4 of 15 dogs (27%) whose saliva samples were positive. The time from sample collection to result was less than 5 hours. Because virus may be absent or present at very low level in both clinical fluids, samples taken for ante-mortem diagnosis cannot definitively rule out rabies.

Etiologies of glomerular diseases in Thailand: a renal biopsy study of 506 cases.

BACKGROUND: The nationwide renal registry has not yet been organized in Thailand, and the literature contains no registry of renal pathologic finding across the Southeast Asian (SEA) countries in the modern era when electron microscopy (EM) is routinely available. OBJECTIVE: The aim of the present study was to examine the prevalence of renal pathology in Thai population. MATERIAL AND METHOD: The authors reviewed the case file and renal biopsy specimens of King Chulalongkorn University Hospital to identify all adult native renal biopsy specimens received from January 2001 to December 2004, investigating prevalence and clinical and histological data. Biopsy of renal graft and in cases of trauma and tumors the authors excluded. Most of the biopsy specimens obtained The authorsre analyzed using light microscopy (LM), immunofluorescense (IF), and EM. Final diagnosis was made for each patient based on clinicopathologic correlations. RESULTS: A total of 506 native renal biopsies were processed during this period, 69.8% were female and 30.2% were male. Their age average was 37 +/- 14.2 (13-80) years. The most common indications for renal biopsy were nephrotic syndrome and SLE (36.8%, 34.5%, respectively), followed by asymptomatic hematuria/proteinuria in 10.9% of patients. Secondary glomerular diseases were dominant against primary diseases in all but elderly age group (>50 years), particularly LN. Among primary glomerular diseases, the prevalence of IgAN, focal segmental glomerulosclerosis, and membranous nephropathy were 31.0%, 24.9%, and 13.1%, respectively. The provisional clinical diagnosis was correct in three fourths (73.2%) of the SLE cases. Postbiopsy complications occurred in 3.3% (17/506). Gross hematuria was seen in 2.3% (12/506), and perinephric hemptoma in 0.79%. Three of them required blood transfusion but none of them died and required an invasive procedure for resolution. The major complications were 2 folds less than regular prevalence (0.6% compared to 1.3%). CONCLUSION: Although the data was collected from single center where EM is routinely performed, the authors believe that IgAN is the commonest primary GN in SEA countries. The authors are looking forward to seeing the nationwide registry data in Thailand and other SEA countries.

Enteric fever-like illness caused by infection with citrobacter amalonaticus.

'Enteric fever' is a potentially fatal, severe systemic disease, which is encountered worldwide. Traditionally, enteric fever refers to a bacteremic illness caused by members of certain Salmonella serotypes, notably: Salmonella typhi, a Gram-negative bacterium, and to a lesser extent, Salmonella paratyphi A, B and C. In addition, other non-salmonella organisms may produce a syndrome clinically indistinguishable from "enteric fever". Brucella sp., Campylobacter sp., Edwardsiella tarda, Enterobacter Cloacae, Escherichia coli, Klebsiella pneumoniae, Providencia alcalifaciens, Pseudomonas sp., Serratia marcescens, Francisella sp. and Yersinia pp have been identified in enteric fever This is, to the best of the authors' knowledge, the first case of Citrobacter to be reported presenting as enteric fever in a normal host in Thailand.

Acute hypercalcemia-induced hypertension: the roles of calcium channel and alpha-1 adrenergic receptor.

OBJECTIVE: To study the mechanism(s) of acute hypercalcemia-induced hypertension in dogs. MATERIAL AND METHOD: Adult male mongrel dogs were intravenously infused with: 1) normal saline solution, 2) CaCl2 solution, 3) CaCl2 + calcium channel blocker (verapamil), 4) CaCl2 + selective alpha-1 adrenergic receptor blocker (prazosin), or 5) CaCl2 + verapamil + prazosin. Either verapamil or prazosin treatment was started at forty minutes before CaCl2 infusion and then was co-administered throughout the three-hour experimental period. Systemic and renal hemodynamics parameters were determined. RESULTS: Infusion of CaCl2 caused increases in mean arterial blood pressure (p < 0.01), total peripheral resistance (p < 0.001), and renal vascular resistance (p < 0.001). Prior treatment with either verapamil or prazosin lowered baseline blood pressure (p < 0.01) and could prevent hypercalcemia-induced hypertension. This occurred accompanying regaining to near normal values of abnormal systemic hemodynamics parameters. Combination of both drugs showed more profound effects, particularly on lowering renal vascular resistance. CONCLUSION: Acute hypercalemic hypertension is caused by an increase in vascular resistance mediated via the direct effect of calcium on vascular smooth muscle as well as the indirect effect of calcium induced hypercatecholaminemia. The stimulatory effect of hypercalcemia on renal vascular resistance is more prominent than that on peripheral vascular resistance.

Oral bacterial flora of dogs with and without rabies: a preliminary study in Thailand.

The authors studied the bacterial flora of the dog oral cavity and of bite wounds, Aerobic bacteria were isolated from mouth swabs of 16 normal and 5 rabid dogs as well as from infected dog-bite wounds from 18 patients. A total of 20 different microbial species were recovered from mouth swab cultures. The most frequently isolated organisms were Klebsiella pneumoniae ssp pneumoniae, Escherichia coli, Staphylococcus aureus, Citrobacter freundii, Enterobacter cloacae, Acinetobacter calcoaceticus, and Pasteurella species. There were no differences in the aerobic bacterial flora between rabid and nonrabid dogs. From the cultures of the bite wound swabs, the authors found that almost all of the organisms identified were part of the normal oral flora of the dog. One or more aerobic bacteria were isolated from the infected dog-bite wounds. Two patients had four, 3 had three, 4 had two, and 6 had one of the nine organisms in their wounds. The predominant species of bacteria involved in infection of bite wounds were, as follows: Staphylococcus aureus, Pasteurella multocida, E. coli, Moraxella species, Pasteurella canis, and Enterobacter cloacae. However, three wound cultures had no aerobic bacterial growth. The results of this study show that the infected bite wounds may contain a mixed bacterial flora that colonize human skin and the oral cavity of dogs.

Medical residency training in the US: important considerations.

The United States attracts medical scholars from abroad. However, the previously open-armed welcome extended to medical residents in America no longer exists for a variety of reasons. A series of barriers based on high educational standards and a rigid system of testing scientific and clinical skills and communication abilities, now tend to eliminate many applicants. Added to this is that American medical colleges now produce a near adequate number of new graduates and that foreign trained residents are often relegated to less desirable programs. These may not provide the level of training expected by the applicant. Less attractive programs are also less likely to enhance the scholar's chances of gaining an academic career and professional recognition on returning home. Applicants for residencies in the US should now be aware that only the best are likely to gain entrance to highly desired posts and to quality fellowships after completing a residency in America. All of this should be weighed against the stress and high costs that are now entailed in obtaining postgraduate medical training in America. This study endeavors to summarize what a young doctor should know about the application process for an American residency position and what he might expect from it.

Magnesium and zinc status in survivors of sudden unexplained death syndrome in northeast Thailand.

Sudden Unexplained Death Syndrome (SUDS) is a major health problem in rural residents of Northeast Thailand. The cause of death in SUDS is suspected to be cardiovascular abnormalities. As magnesium (Mg) and zinc (Zn) deficiency contribute significantly to several cardiovascular diseases, we investigated the Mg- and Zn-status of patients with sudden respiratory distress and cardiac arrest who had survived resuscitation attempts or a near-SUDS episode (N-SUDS). The following subjects were enrolled: 12 N-SUDS inhabitants of rural Northeast Thailand (rural group 1, R1), 13 rural villagers with no past history of N-SUDS (rural group 2, R2), 15 urban Northeasterners (urban group 1, U1); 13 Bangkokians (urban group 2, U2). All subjects were free of structural heart disease. Magnesium and zinc were assessed by atomic absorption spectrophotometry of samples of plasma, red blood cells (RBC), white blood cells (WBC), and 24-hour urine. The mean levels of magnesium in the RBC, WBC, and 24-hour urine of N-SUDS patients (R1) were significantly lower than those of the urban groups (U1 and U2), while the plasma levels did not show any differences. When comparing the Zn-status of R1 with that of the urban groups (U1 and U2), the plasma, RBC, and WBC levels were found to be significantly lower in R1 (except for the RBC-Zn of the U1 group), while the 24-hour urine levels was higher. Although the magnesium and zinc parameters were not significantly different between the rural groups R1 and R2, the prevalence of hypomagnesuria (<2.2 mmol/day), hypozincemia (<9.7 micromol/l), and hyperzincuria (>10.7 micromol/day) was higher in the R1 group. These findings suggest that the homeostasis of both magnesium and zinc is altered in N-SUDS patients. Similar alterations, to a lesser degree, were observed in those people living in the same rural environment (R2).

Leptospirosis in northeastern Thailand: hypotension and complications.

During an outbreak of leptospirosis in northeastern Thailand, 148 patients with serologically diagnosed leptospirosis were seen in Loei Hospital. The clinical features were consistent with those described for the classic manifestation of the disease. However, hypotension was a common finding: noted in 94 patients (64%) upon admission or early in the course of the disease. Of these hypotensive patients, 64 (68%) had impaired renal function: 30 patients (32%) had prerenal azotemia and 34 (36%) were in renal failure. Pulmonary complications, including pulmonary edema, hemorrhage, ARDS, and interstitial pneumonitis, occurred in 22% of patients and were often associated with renal failure. A clear association existed between hypotension and renal failure and pulmonary complications. The overall mortality rate was 3.4%. The causes of death were pulmonary complications, renal failure, and sepsis. The death rate among patients with complications was 11.6%. Blood exchange, in addition to conventional treatment, was beneficial in severe leptospirosis with complications and hyperbilirubinemia.