Relationship between body condition of American alligators and water depth in the Everglades, Florida

Feeding opportunities of American alligators (Alligator mississippiensis) in freshwater wetlands in south Florida are closely linked to hydrologic conditions. In the Everglades, seasonally and annually fluctuating surface water levels affect populations of aquatic organisms that alligators consume. Since prey becomes more concentrated when water depth decreases, we hypothesized an inverse relationship between body condition and water depth in the Everglades. On average, condition of adult alligators in the dry season was significantly higher than in the wet season, but this was not the case for juveniles/subadults. The correlation between body condition and measured water depth at capture locations was weak; however, there was a significant negative correlation between the condition and predicted water depth prior to capture for all animals except for spring juveniles/subadults which had a weak positive condition–water depth relationship. Overall, a relatively strong inverse correlation occurred at 10–49 days prior to the capture day, suggesting that current body condition of alligators may depend on feeding opportunities during that period. Fitted regression of body condition on water depth (mean depth of 10 days when condition-water depth correlation was greatest) resulted in a significantly negative slope, except for spring adult females and spring juveniles/subadults for which slopes were not significantly different from zero. Our results imply that water management practices may be critical for alligators in the Everglades since water depth can affect animal condition in a relatively short period of time.     

Growth rates of Chinese and American alligators

Growth rates in two closely related species, Alligator mississippiensis (American alligator) and Alligator sinensis (Chinese alligator), were compared under identical conditions for at least 1 year after hatching. When hatched, Chinese alligators were approximately 2/3 the length and approximately 1/2 the weight of American alligator hatchlings. At the end of 1 year of growth in captivity in heated chambers, the Chinese alligators were approximately 1/2 as long and weighed approximately 1/10 as much as American alligator yearlings. When the animals were maintained at 31 degrees C, Chinese alligator food consumption and length gain rates dropped to near zero during autumn and winter and body weights decreased slightly, apparently in response to the change in day length. At constant temperature (31 degrees C), food consumption by American alligators remained high throughout the year. Length gain rates in American alligators decreased slowly as size increased, but were not affected by photoperiod. Daily weight gains in American alligators increased steadily throughout the year. In autumn, provision of artificial light for 18 h a day initially stimulated both length and weight gain in Chinese alligators, but did not affect growth in American alligators. Continuation of the artificial light regimen seemed to cause deleterious effects in the Chinese alligators after several months, however, so that animals exposed to the normal light cycle caught up to and then surpassed the extra-light group in size. Even after removal of the artificial light, it was several months before these extra-light animals reverted to a normal growth pattern. These findings may be of interest to those institutions engaged in captive growth programs intended to provide animals for reintroduction to the wild or to protected habitat.     

Pathology, physiologic parameters, tissue contaminants, and tissue thiamine in morbid and healthy central Florida adult American alligators (Alligator mississippiensis)

An investigation of adult alligator (Alligator mississippiensis) mortalities in Lake Griffin, central Florida, was conducted from 1998-2004. Alligator mortality was highest in the months of April and May and annual death count peaked in 2000. Bacterial pathogens, heavy metals, and pesticides were not linked with the mortalities. Blood chemistry did not point to any clinical diagnosis, although differences between impaired and normal animals were noted. Captured alligators with signs of neurologic impairment displayed unresponsive and uncoordinated behavior. Three of 21 impaired Lake Griffin alligators were found to have neural lesions characteristic of thiamine deficiency in the telencephalon, particularly the dorsal ventricular ridge. In some cases, lesions were found in the thalamus, and parts of the midbrain. Liver and muscle tissue concentrations of thiamine (vitamin B(1)) were lowest in impaired Lake Griffin alligators when compared to unimpaired alligators or to alligators from Lake Woodruff. The consumption of thiaminase-positive gizzard shad (Dorosoma cepedianum) is thought to have been the cause of the low tissue thiamine and resulting mortalities.     

Organochlorine pesticides and thiamine in eggs of largemouth bass and American alligators and their relationship with early life-stage mortality

Thiamine deficiency has been linked to early mortality syndrome in salmonids in the Great Lakes. This study was conducted to compare thiamine concentrations in American alligators (Alligator mississippiensis) and Florida largemouth bass (Micropterus salmoides floridanus) eggs from sites with high embryo mortality and high exposure to organochlorine pesticides (OCPs) (Lakes Apopka and Griffin, and Emeralda Marsh, Florida, USA) to those from sites that have historically exhibited low embryo mortality and low OCPs (Lakes Woodruff and Orange, Florida). During June-July 2000, 20 alligator clutches were collected from these sites, artificially incubated, and monitored for embryo mortality. Thiamine and OCPs were measured in one egg/clutch. During February 2002, 10 adult female bass were collected from Emeralda Marsh and Lake Woodruff and mature ovaries analyzed for thiamine and OCP concentrations. Although ovaries from the Emeralda Marsh bass contained almost 1,000-fold more OCPs compared with the reference site, Lake Woodruff, there were no differences in thiamine concentrations between sites (11,710 vs. 11,857 pmol/g). In contrast, alligator eggs from the reference site had five times the amount of thiamine compared with the contaminated sites (3,123 vs. 617 pmol/g). Similarly, clutches with >55% hatch rates had significantly higher concentrations of thiamine compared with clutches with <54% hatch rates (1,119 vs. 201 pmol/g). These results suggest that thiamine deficiency might be playing an important role in alligator embryo survival but not in reproductive failure and recruitment of largemouth bass. The cause(s) of this thiamine deficiency are unknown but might be related to differences in the nutritional value of prey items across the sites studied and/or to the presence of high concentration of contaminants in eggs.     

Methicillin-resistant Staphylococcus aureus infection is associated with increased mortality

Methicillin resistance is a widespread and major source of treatment complication in Staphylococcus aureus infections. Whether infections with methicillin-resistant S. aureus are associated with a worse clinical outcome, such as higher mortality, has remained controversial. Analyzing data from a large, global multicenter study, Hanberger et al. demonstrate that methicillin-resistant S. aureus infections are associated with approximately 50% higher mortality in the intensive care unit and significantly more frequent among critically ill patients than infections with methicillin-susceptible S. aureus. These findings call for the implementation or continuation of active methicillin-resistant S. aureus surveillance measures.     

Low mitochondrial DNA variation among American alligators and a novel non-coding region in crocodilians

We analyzed 1317-1823 base pairs (bp) of mitochondrial DNA sequence beginning in the 5' end of cytochrome b (cyt b) and ending in the central domain of the control region for 25 American alligators (Alligator mississippiensis) and compared these to a homologous sequence from a Chinese alligator (A. sinensis). Both species share a non-coding spacer between cyt b and tRNA(Thr). Chinese alligator cyt b differs from that of the American alligator by 17.5% at the nucleotide level and 13.8% for inferred amino acids, which is consistent with their presumed ancient divergence. Only two cyt b haplotypes were detected among the 25 American alligators (693-1199 bp surveyed), with one haplotype shared among 24 individuals. One alligator from Mississippi differed from all other alligators by a single silent substitution. The control region contained only slightly more variation among the 25 American alligators, with two variable positions (624 bp surveyed), yielding three haplotypes with 22, two, and one individuals in each of these groups. Previous genetic studies examining allozymes and the proportion of variable microsatellite DNA loci also found low levels of genetic diversity in American alligators. However, in contrast with allozymes, microsatellites, and morphology, the mtDNA data shows no evidence of differentiation among populations from the extremes of the species range. These results suggest that American alligators underwent a severe population bottleneck in the late Pleistocene, resulting in nearly homogenous mtDNA among all American alligators today.     

New-onset atrial fibrillation in sepsis is associated with increased morbidity and mortality

BackgroundThe development of new-onset atrial fibrillation in sepsis has been associated with adverse outcomes.MethodsA systematic literature search was conducted to retrieve articles that investigated the association of new-onset atrial fibrillation in patients diagnosed with sepsis. The primary outcome of interest was the pooled risk ratio (RR) of in-hospital mortality in patients with new-onset atrial fibrillation and sepsis.ResultsSix studies included 3100 patients with new-onset atrial fibrillation in sepsis and 36,900 patients without new-onset atrial fibrillation in sepsis. The pooled RR for in-hospital mortality was 1.45 (95 % CI 1.32–1.60, p < 0.00001, I^2 =24 %). New-onset atrial fibrillation was also associated with increased ICU mortality, ICU and in-hospital length of stay and stroke. New-onset atrial fibrillation occurred more in the elderly, those with a prior history of cardiovascular and respiratory disease, and those with increased severity of illness.ConclusionProspective randomised trials are needed to clarify the significance of new-onset atrial fibrillation in sepsis, optimal treatment strategies for these patients, and the benefit of systemic anticoagulation. Physicians should be aware that new-onset atrial fibrillation in sepsis is not merely an observed temporary arrhythmia but a marker of poor prognosis and should be managed accordingly.     

Cytomegalovirus infection is associated with increased mortality in the older population

Cytomegalovirus (CMV) is a common herpesvirus infection and stimulates the expansion of very large numbers of CMV‐specific T cells that reduce the CD4/CD8 ratio and suppress the number of naïve T cells. CMV infection has been associated with frailty and impaired survival. We investigated the correlates of CMV and the impact of the CMV infection on mortality within a cohort of 511 individuals aged at least 65 years who were followed up for 18 years. The mean age of the participants was 74 years of which 70% were CMV‐seropositive. CMV was strongly linked to socio‐economic status, and CMV infection increased the annual mortality rate by 42% (Hazard ratio = 1.42, 95% CI: 1.11–1.76 after adjusting for age, sex and baseline socio‐economic and health variables) corresponding to 3.7 years lower life expectancy from age 65. Infection was associated with a near doubling of cardiovascular deaths, whereas there was no increase in mortality from other causes. These results show that CMV infection markedly increases the mortality rate in healthy older individuals due to an excess of vascular deaths. These findings may have significant implications for the study of immune senescence and if confirmed more generally could have important implications for measures to optimize the health of the elderly.     

Risk factors associated with increased mortality among HIV infected children initiating antiretroviral therapy (ART) in South Africa

Objective

To identify demographic and clinical risk factors associated with mortality after initiation of antiretroviral therapy (ART) in a cohort of human immunodeficiency (HIV) infected children in KwaZulu-Natal, South Africa.

Methods

We performed a retrospective cohort study of 537 children initiating antiretroviral therapy at McCord Hospital in KwaZulu-Natal, South Africa. Data were extracted from electronic medical records and risk factors associated with mortality were assessed using Cox regression analysis.

Results

Overall there were 47 deaths from the cohort of 537 children initiating ART with over 991 child-years of follow-up (median 22 months on ART), yielding a mortality rate of 4.7 deaths per 100 child years on ART. Univariate analysis indicated that mortality was significantly associated with lower weight-for-age Z-score (p<0.0001), chronic diarrhea (p = 0.0002), lower hemoglobin (p = 0.002), age <3 years (p = 0.003), and CD4% <10% (p = 0.005). The final multivariable Cox proportional hazards mortality model found age less than 3 years (p = 0.004), CD4 <10% (p = 0.01), chronic diarrhea (p = 0.03), weight-for-age Z-score (<0.0001) and female gender as a covariate varying with time (p = 0.03) all significantly associated with mortality.

Conclusion

In addition to recognized risk factors such as young age and advanced immunosuppression, we found female gender to be significantly associated with mortality in this pediatric ART cohort. Future studies are needed to determine whether intrinsic biologic differences or socio-cultural factors place female children with HIV at increased risk of death following initiation of ART.     

Necropsy findings in American alligator late-stage embryos and hatchlings from northcentral Florida lakes contaminated with organochlorine pesticides

Increased American alligator (Alligator mississippiensis) embryo and neonatal mortality has been reported from several northcentral Florida lakes contaminated with old-use organochlorine pesticides (OCPs). However, a clear relationship among these contaminants and egg viability has not been established, suggesting the involvement of additional factors in these mortalities. Thus, the main objective of this study was to determine the ultimate cause of mortality of American alligator late-stage embryos and hatchlings through the conduction of detailed pathological examinations, and to evaluate better the role of OCPs in these mortalities. Between 2000 and 2001, 236 dead alligators were necropsied at or near hatching (after approximately 65 days of artificial incubation and up to 1 mo of age posthatch). Dead animals were collected from 18 clutches ranging in viability from 0% to 95%. Total OCP concentrations in yolk ranged from approximately 100 to 52,000 microg/kg, wet weight. The most common gross findings were generalized edema (34%) and organ hyperemia (29%), followed by severe emaciation (14%) and gross deformities (3%). Histopathologic examination revealed lesions in 35% of the animals, with over half of the cases being pneumonia, pulmonary edema, and atelectasis. Within and across clutches, dead embryos and hatchlings compared with their live cohorts were significantly smaller and lighter. Although alterations in growth and development were not related to yolk OCPs, there was an increase in prevalence of histologic lesions in clutches with high OCPs. Overall, these results indicate that general growth retardation and respiratory abnormalities were a major contributing factor in observed mortalities and that contaminants may increase the susceptibility of animals to developing certain pathologic conditions.     

Aerobic metabolism of American alligators, Alligator mississippiensis, under standard conditions and during voluntary activity

We measured the rate of consumption of oxygen by alligators in a dry metabolic chamber and in a tank of water where they were free to dive and surface at will at 10-35 degrees C, a range spanning most of the body temperatures experienced by alligators in nature. Neither the standard metabolic rate nor the rate of oxygen consumption during one hour of sustained, voluntary activity varied with body mass, month of the year, duration of fasting before measurement, or experimental condition (terrestrial vs aquatic). Voluntary diving is not accompanied by any reduction in standard metabolic rate; these results and those of others suggest that the "diving reflex" of alligators is probably employed only in emergencies. Spontaneous activity for one hour is accompanied by a 1.9-4.4 fold rise in oxygen consumption; this factorial increase is less than that for other reptiles induced to maximal activity for brief intervals. Both standard and active oxygen consumption rise significantly with body temperature.     

Burrowing fly larvae (Philornis porteri) associated with mortality of eastern bluebirds in Florida

We investigated mortality among nestling eastern bluebirds (Sialia sialis) in Polk and Highlands counties, Florida (USA) in 1999-2001. At least six species of maggots from three families of muscoid flies, Calliphoridae, Sarcophagidae, and Muscidae were found associated with the nestlings. Philornis porteri, the only species of obligate bird parasite collected, was found in the contents of two nests, in the ear canal and the musculature of the jaw of one nestling, and in the abdominal subcutis of another. This is the first record of bluebird parasitism by P. porteri. Although some nestlings were infested by tissue-invading fly larvae antemortem, the role of these maggots in the overall mortality was not clear.     

Hydrilla control with split treatments of fluridone in Lake Harris, Florida

After several unsuccessful management efforts, a split treatment of fluridone was applied to the 6700 ha Lake Harris in March and June 1987, at a rate of 3.4 kg ha^–1 (680 and 340 kg fluridone, respectively) to two 3 m deep, hydrilla-infested bays. Fluridone concentrations in the water were sampled following the June treatment. Average fluridone concentrations were 2.1 µg l^–1 prior to this second application, and a maximum concentration of 30.2 µg l^–1 was detected in the treated area on the day following application. Fluridone residues dissipated out of the plot quickly due to dilution but concentrations declined lake-wide more slowly, following a logarithmic model, with an estimated fluridone half-life of 97 days. Control of hydrilla in Lake Harris resulted from the long exposure (over 25 weeks due to the split application) to fluridone concentrations of 2 µg l^–1, well below the maximum labelled rate of 150 µg l^–1.     

American wigeon mortality associated with turf application of diazinon AG500.

Nine fairways of a golf course located in Bellingham, Washington were treated with diazinon AG500 at a target application rate of 2.2 kg active ingredient (AI) per ha. The chemical application with a "boomless" sprayer resulted in a variable distribution of diazinon residues on the turf (associated with a deep thatch layer) that ranged from 1.0 to 6.2 kg AI/ha. The diazinon-treated turf was irrigated with 1.3 cm of water immediately following application. The post-irrigation diazinon residue levels ranged from 100 to 333 ppm (mean = 209; SD = 88; n = 8). These residue levels were higher than expected based on results of turf studies in other regions of the United States. Eighty-five American wigeon (Anas americana) died after grazing on one treated fairway on the day of application following irrigation. The brains of all 85 wigeon were analyzed for acetylcholinesterase (AChE) activity. Wigeon that died on the study area (n = 85) showed 44% to 87% depression of AChE (mean = 76%; SD = 7.1%) when compared to control wigeon (n = 3; AChE Activity = 1.86) AChE levels. Upper GI tract contents of 15 of the 85 dead wigeon contained 0.96 to 18.1 ppm diazinon. Extensive carcass searches revealed no other avian mortality attributable to diazinon toxicity on the treated study area. Although initial post-irrigation diazinon residues in grass samples were higher than expected, diazinon levels in grass samples on day seven post-application had declined to an average of 29 ppm. American wigeon appear to be vulnerable to exposure to diazinon.(ABSTRACT TRUNCATED AT 250 WORDS)     

Altered histology of the thymus and spleen in contaminant-exposed juvenile American alligators

Morphological differences in spleen and thymus are closely related to functional immune differences. Hormonal regulation of the immune system has been demonstrated in reptilian splenic and thymic tissue. Spleens and thymus were obtained from juvenile alligators at two reference sites in Florida, USA: Orange Lake and a National Wildlife Refuge, Lake Woodruff, as well as from a contaminated lake, Lake Apopka. Lake Apopka has been extensively polluted with agricultural pesticides. Tissues were prepared for histological analysis to determine if previously detected endocrine abnormalities associated with contaminant exposure might also be reflected in morphological differences in splenic and thymic structures important for immunological response. Similar tissues were taken from captive-raised juvenile female alligators (3 years old) that were hatched from eggs collected on Lake Woodruff and Lake Apopka. Differences in thymic ratios (medulla/cortex) were found among alligators collected from the two lakes (P = 0.0051). Alligators from Lake Apopka had smaller thymic ratios than animals from either reference lake. Males from Lake Woodruff had significantly smaller lymphocyte sheaths in the spleen than females (P = 0.0009), indicative of a normal sexual dimorphism. Lymphocyte sheath width differed among females obtained from the three lakes, with females from Lake Apopka having the smallest sheath width and those from Orange Lake having the largest. Malpighian body area was largest in alligators from Orange Lake, intermediate in Lake Woodruff, and smallest in Lake Apopka. In contrast to that observed for wild-caught animals, no difference was found in the thymic medulla/cortex ratio of captive-raised female alligators (P = 0.378). Captive-raised female alligators from Lake Apopka and Lake Woodruff displayed lake-associated differences in lymphocyte sheath width as observed in wild animals; Lake Apopka alligators had smaller lymphocyte sheath width compared to Woodruff alligators (P = 0.0396). In contrast to wild-caught animals, area of the Malpighian bodies did not differ by lake in the captive-raised female alligators (P = 0.066). The enlarged thymic cortex suggests a change in T-lymphocyte maturation within the thymus of alligators from a contaminated environment, Lake Apopka. The results point to alterations in the histology of the thymus and spleen. Further studies are required to examine the functional significance of these observations.     

The lipid accumulation product is associated with increased mortality in normal weight postmenopausal women

Lipid accumulation product (LAP) is an emerging cardiovascular risk factor, which is calculated from waist circumference (WC) and triglyceride (TG) levels. The aim of this study was to elucidate the relationship between LAP and cardiovascular mortality as well as the presence of type 2 diabetes with respect to gender-specific differences. We determined WC and fasting TG levels and the cardiovascular and metabolic phenotypes coronary artery disease (CAD), hypertension, metabolic syndrome, and diabetes mellitus in 2,279 men and 875 postmenopausal women who were routinely referred to coronary angiography. The LAP was calculated as (WC (cm)--65) × (TG (mmol/l)) for men and as (WC (cm)--58) × (TG (mmol/l)) for women. LAP levels were independently associated with congestive heart failure mortality in all postmenopausal women and with all-cause mortality in diabetic postmenopausal women but not in men. Multivariable-adjusted hazard ratios (with 95% confidence intervals) for all-cause, cardiovascular, and congestive heart failure mortality in the third compared to the first LAP tertile were 4.28 (1.94-9.44; P < 0.001), 3.47 (1.28-9.40; P = 0.015), and 10.77 (1.21-95.88; P = 0.033), respectively, in normal weight postmenopausal women, whereas no significant associations were found in men. LAP levels were highly associated with type 2 diabetes in all subjects, postmenopausal women, and men. High LAP values are predictive of mortality independently of other cardiovascular risk factors in normal weight and diabetic postmenopausal women but not in men. Type 2 diabetes (T2DM) was highly associated with LAP in women and men. Our study validates an inexpensive and simple risk profiling that may allow identifying postmenopausal women at high cardiovascular risk.     

Risk factors associated with mortality from white-nose syndrome among hibernating bat colonies

White-nose syndrome (WNS) is a disease responsible for unprecedented mortality in hibernating bats. First observed in a New York cave in 2006, mortality associated with WNS rapidly appeared in hibernacula across the northeastern United States. We used yearly presence-absence data on WNS-related mortality among hibernating bat colonies in the Northeast to determine factors influencing its spread. We evaluated hazard models to test hypotheses about the association between the timing of mortality and colony-level covariates, such as distance from the first WNS-affected site, colony size, species diversity, species composition and type of hibernaculum (cave or mine). Distance to origin and colony size had the greatest effects on WNS hazard over the range of observations; the type of hibernaculum and species composition had weaker effects. The distance effect showed a temporal decrease in magnitude, consistent with the pattern of an expanding epizootic. Large, cave-dwelling bat colonies with high proportions of Myotis lucifugus or other species that seek humid microclimates tended to experience early mortality. Our results suggest that the timing of mortality from WNS is largely dependent on colony location, and large colonies tend to be first in an area to experience high mortality associated with WNS.