Mortality of Rocky Mountain elk in Michigan due to meningeal worm

Mortality from cerebrospinal parelaphostrongylosis caused by the meningeal worm (Parelaphostrongylus tenuis) has been hypothesized to limit elk (Cervus elaphus nelsoni) populations in areas where elk are conspecific with white-tailed deer (Odocoileus virginianus). Elk were reintroduced into Michigan (USA) in the early 1900s and subsequently greatly increased population size and distribution despite sympatric high-density (>or=12/km2) white-tailed deer populations. We monitored 100 radio-collared elk of all age and sex classes from 1981-94, during which time we documented 76 mortalities. Meningeal worm was a minor mortality factor for elk in Michigan and accounted for only 3% of mortalities, fewer than legal harvest (58%), illegal kills (22%), other diseases (7%), and malnutrition (4%). Across years, annual cause-specific mortality rates due to cerebrospinal parelaphostrongylosis were 0.033 (SE=0.006), 0.029 (SE=0.005), 0.000 (SE=0.000), and 0.000 (SE=0.000) for calves, 1-yr-old, 2-yr-old, and >or=3-yr-old, respectively. The overall population-level mortality rate due to cerebrospinal parelaphostrongylosis was 0.009 (SE=0.001). Thus, meningeal worm had little impact on elk in Michigan during our study despite greater than normal precipitation (favoring gastropods) and record (>or=14 km2) deer densities. Further, elk in Michigan have shown sustained population rates-of-increase of >or=18%/yr and among the highest levels of juvenile production and survival recorded for elk in North America, indicating that elk can persist in areas with meningeal worm at high levels of population productivity. It is likely that local ecologic characteristics among elk, white-tailed deer, and gastropods, and degree of exposure, age of elk, individual and population experience with meningeal worm, overall population vigor, and moisture determine the effects of meningeal worm on elk populations.     

Meningeal worm in a reintroduced elk population in Kentucky

Meningeal worm (Parelaphostrongylus tenuis) has been implicated in the failure of several elk (Cervus elaphus) restoration attempts in the eastern United States. However, limited post-release monitoring and a paucity of published literature prevents a clear understanding of this parasite's role in past failures. During winters of 1997-2001, the Kentucky Department of Fish and Wildlife Resources translocated 1,044 elk from western states to eastern Kentucky (USA) in an effort to restore a free-ranging population. We monitored 521 radio-collared elk over 4 yr to determine the impact meningeal worm had on population establishment. Thirty (23%) of 129 non-capture related mortalities were attributed to meningeal worm. Twenty-two (73%) of these meningeal worm-caused mortalities were animals < 3 yr old. If younger elk born in Kentucky suffer higher mortality rates than older translocated elk, the population growth observed during the initial years of restoration may be temporary. Additional research is necessary to determine the influence meningeal worm will have on elk population growth in Kentucky.     

Effects of Winter Ticks and Internal Parasites on Moose Survival in Vermont,USA

Moose (Alces alces) have experienced considerable declines along the periphery of their range in the northeastern United States. In Vermont, the population declined 45% from 2010 to 2017 despite minimal hunter harvest and adequate habitat. Similarly, nearby populations recently experienced epizootics characterized by >50% mortality. Declines have largely been associated with the effects of winter ticks (Dermacentor albipictus), but uncertainty exists about the effects of environmental and other parasite-related conditions on moose survival. We examined patterns of moose survival among a radio-collared population (n = 127) in Vermont from 2017 to 2019. Our objectives were to estimate causes of mortality and model survival probability as a function of individual and landscape variables for calves (<1 yr) and adults (≥1 yr). Observed adult survival was 90% in 2017, 84% in 2018, and 86% in 2019, and winter calf survival was 60% in 2017, 50% in 2018, and 37% in 2019. Winter tick infestation was the primary cause of mortality (91% of calves, 25% of adults), and 32% of all mortalities had evidence of meningeal worm (Parelaphostrongylus tenuis). Other sources of mortality such as vehicles, harvest, predation, deep snow, and other parasitic infections were negligible. The best supported calf model included sex differences and negative effects of tick engorgement (%/week) and parasite level (roundworm and lungworm). The best supported adult model included the effect of cumulative tick engorgement (cumulative %/week), which negatively affected survival. Our results indicate that winter tick engorgement strongly affects survival, and is probably compounded by the presence of meningeal worm and other parasites. Reduced tick effects may be achieved by decreasing moose density through harvest and managing late winter habitat to minimize tick density. Management of white-tailed deer (Odocoileus virginianus) density may also affect the transmission of meningeal worm. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

Risk of early death in extremely overweight young men.

The effect of pronounced obesity in youth on later mortality was studied in 1239 men with extreme overweight, defined as a weight/height 2 greater than or equal to 31 kg/m2, in the population of 331 919 men liable for military service in the Copenhagen area during the period 1943-1977. A random sample of 2948 drawn from the remaining study population served as a control group. All men were followed up until November 1980, by which time 33 deaths had occurred among the extremely overweight subjects compared with 89 in the control group. This gave a mortality ratio (observed to expected number of deaths) of 1.14 (95% confidence limit 0.91-1.40) for controls with a significantly greater mortality of 1.73 (95% confidence limit 1.20-2.41) for obese subjects. The relative risk, estimated from the survival time distributions, was fairly constant around 1.6 throughout the 37 years of observation. Taking into account age at and year of entry in a regression analysis did not change the relative mortality risk. The proportion of natural death was significantly higher in the obese group than in the control group until the age of 30 but not thereafter. Pronounced obesity in youth is a health hazard, manifesting itself particularly in a distinct increase in mortality from natural causes in early adulthood.     

Cerebrospinal nematodiasis caused by Parelaphostrongylus tenuis in Angora goats in Texas.

A natural infection of meningeal worm (Parelaphostrongylus tenuis) accounted for the death of 11 of 17 (65%) Angora goats in a study in South Texas during 1975. Clinical signs, gross pathology and histopathology in Angoras were similar to other abnormal hosts.     

The UK cardiac surgical register, 1977-82.

Data for 1977-82 obtained from the Cardiac Surgical Register, established by the Society of Thoracic and Cardiovascular Surgeons of Great Britain and Northern Ireland in 1977, were analysed for trends in incidence and mortality of cardiac surgery and regional workload in the United Kingdom. Operative mortality for most types of cardiac operation showed a general decline. The numbers of operations performed for valvular and congenital heart disease had remained unchanged, but a striking increase had occurred in the number of coronary bypass graft operations: 2297 in 1977 to 6008 in 1982. The figure for 1982, representing an annual rate of 107 operations per million population, was still well below that for other countries such as Australia (410 per million in 1982) and the United States (750 per million in 1981). A wide variation was seen in the regional provision of cardiac surgical services within the United Kingdom. This was particularly appreciable for coronary bypass graft surgery, in which there was a 10-fold difference in numbers of operations performed between the various regions. The UK Cardiac Surgical Register provides an important source of information on trends within the specialty that could well be followed by other surgical specialties.     

Influence of host strain and helminth isolate on the first phase of the relationship between rats and Moniliformis moniliformis (Acanthocephala)

Eleven trials, involving 440 rats bred from 3 laboratory strains and worms from 4 isolates of Moniliformis moniliformis, were carried out with each rat receiving an oral dose of 15 cystacanths. The results showed that the infectivity of the cystacanths was not affected by their age (range 55-194 days) or by their density per cockroach during development (16.1-88.6 cystacanths per cockroach). The numbers of worms per rat recovered at 35 days postinfection (p.i.) were shown to be related to rat strain, with highly inbred strains (PVG and F344) being more supportive of numbers of worms than an outbred Wistar strain. There was no evidence to suggest that the sex of the rats had any influence on the numbers of worms recovered at 35 days p.i. Evidence was obtained to suggest that smaller (younger) rats are likely to support more worms on average than larger (older) rats. There was no evidence of any relationship between worm weight and numbers of worms present per rat on day 35 p.i. Generally, rat strain had little effect on the dry weight (growth) of male M. moniliformis, in contrast to observations made for female worms. The greatest range of worm weights was observed from the recent isolate of the worm (1982) as compared with the well established isolate (1956) and the rats that supported most worms differed from those that harbored the largest worms. Rat sex was not observed to be associated with worm weight. The frequency distributions of numbers of M. moniliformis per rat were not described readily by the negative binomial distribution.     

Parelaphostrongyliasis in white-tailed deer in Missouri

The heads of 137 white-tailed deer (Odocoileus virginianus) were collected on the opening day of the 1996 Missouri (USA) fire-arms deer season and surveyed for the presence of meningeal worm (Parelaphostrongylus tenuis). Eighteen percent of the deer examined were infected. Mean intensity of infection was 2.0 (range 1-7). There were no significant differences of infection or mean intensity when deer were classified and compared according to sex or age class.     

Predation risk and habitat selection in the persistence of a remnant caribou population

Summary A small caribou herd of 24–77 animals resided on Pic Island (1138 ha) in Lake Superior from 1976 to 1984. Most of the caribou populations on the adjacent mainland had gone extinct earlier in this century. We tested three hypotheses for the persistence of this remanant population: (1) there was more forage available on the island than the mainland, (2) the animals on the island were isolated from white-tailed deer and did not develop the meningeal worm infection, and (3) there was less predation by wolves on the island. Forage was more abundant on the mainland than on Pic Island. The eggs of meningeal worms were not found in the feces of deer on the mainland or Pic island. Wolves seldom visited the island and when they did there was escape habitat available for the caribou. We concluded that the herd persisted because of this reduced predation risk and that the animals were prepared to select a reduced variety and phytomass of forage to remain for long periods in the relatively safe island habitat. When the animals did visit the mainland to feed they sclected forbs that provided a large bite size. On the island food supplies were too meager to select plants that gave a large bite size and the caribou spent long intervals feeding. Caribou by using habitats with a large phytomass and selecting for large bite size should minimize their time feeding which would allow them more time to watch for predators.     

斑苦竹无性系种群克隆繁殖的动态与调节研究

本文依据了JLHarper (1977)的构件生物(madular organism)种群理论,将某一特定生境内的斑苦竹竹子的集合作为一个无性系种群,研究了它的克隆繁殖构件的数量动态,以及克隆繁殖与无性系基株年龄和分株密度的关系。结果表明:斑苦竹以Ⅲ龄级基株形成的克隆繁殖构件(笋芽)数量最多,以后,随龄级的增大而逐渐减少。发笋数、退笋数和成竹数均与无性系分株密度相关,它们的最适密度都为2.5×10⁴株/ha。退笋率和成竹率与繁殖构件的出土时间呈直线相关关系。退笋率模型:D=27.253+0.702t(R²=0.636)成竹率模型:M=72.662-0.701t(R²=0.634)     

Schistosoma mansoni: the effect of adrenalectomy on the murine model

Adrenal steroid hormones have been implicated, among others, as one of the most important host factors controlling the onset, establishment, and pathogenesis of schistosomiasis. They appear to inhibit oviposition by Schistosoma mansoni both in vitro and in vivo, and their effect is greatly enhanced when administered in combination with a schistosomicidal drug. Therefore, we hypothesized that adrenalectomy would greatly affect the course of the murine schistosomiasis infection. To test this hypothesis, adrenalectomized mice (Adx) infected with S. mansoni were compared with intact infected and sham-infected controls concerning their mortality rate, numbers of male and female worms, number of eggs, and liver pathology. Compared with controls, Adx infected mice showed an increase of 50% in the mortality rate, as well as 1.7-3 times as many adult worms and twice as many ova per worm pair in their liver. Thus, for the first time, there is evidence that lack of adrenal steroids mediate an increment of the adult worm burden and promote worm fecundity in vivo. The present work was done to test the hypothesis that lack of adrenal steroids enhances adult worm attrition, possibly by their direct effect on the parasite, and by upregulating or downregulating innate and adaptive immune responses.     

西双版纳不同斑块望天树种群的密度、结构和生物量

 根据5个不同斑块的野外调查数据,分析了残存分布在西双版纳的国家一级保护稀有树种望天树（Parashorea chinensis）的种群密度与数量、 年龄结构与生物量动态, 组建了不同生长发育阶段的望天树个体生长与年龄的回归模型、个体生物量模型及种群年龄结构模型, 编制了不同 斑块的望天树种群及整个种群的静态生命表、存活曲线和年龄结构图。结果表明,不同斑块的望天树种群因种群年龄及所受到的干扰方式的不 同,其种群密度和年龄结构差异很大,不同年龄阶段的死亡率也不同。面积最小的斑块缺乏成熟个体,并出现龄级结构缺省的现象。不同斑块 局部种群的生物量随林龄的变化近似于Logistic增长,但各斑块局部种群的最大生物量以及生物量随时间的动态变化有所不同。整个种群的年 龄结构为稳定增长型种群,1～60龄的种群个体的死亡率随林龄的增加而下降,60～150龄的个体死亡率随林龄的增加而上升,180 龄后种群呈 现生理衰退,个体出现死亡高峰。种群的生物量在180 龄前呈Logistic 增长,此后,生物量下降。部分斑块受到严重的人为干扰,已严重威胁 其局部种群的生存。     

Epizootiological features of avian cholera on the north coast of California

An avian cholera (Pasteurella multocida) epizootic was observed among wildfowl at the Centerville Gun Club, Humboldt County, California (USA) in January 1978. Compared to their live populations and use of the area, coots (Fulica americana) died in proportionately greater numbers than any other species. Coots collected by gunshot were evaluated for sex and age composition, and morphometry from November 1977 through mid-January 1978 at this site. There was no substantial difference in the sex, age or morphometry between birds dying of avian cholera and from those dying from gunshot. Assuming coots dying of gunshot are representative of the general population, it appears there was little selection among coots by P. multocida. There was evidence for a sequential mortality similar to that reported previously at this site: coots were the first birds to die, followed by American wigeon (Anas americana) and northern pintails (A. acuta acuta); northern shovelers (A. clypeata) and mallards (A. platyrhynchos) died late in the epizootic.     

Mortality of fallow deer (Dama dama) experimentally-infected with meningeal worm, Parelaphostrongylus tenuis.

Six fallow deer (Dama dama) fawns died after receiving 25 to 150 infective larvae of Parelaphostrongylus tenuis. Fawns given higher doses usually died sooner (6 to 23 days) than those given lower doses (54 to 67 days). Early deaths were associated with severe acute peritonitis resulting from perforation of the intestinal wall; later deaths were associated with paralysis and inability to rise. Numerous adult P. tenuis were found within neural tissues of the brain and spinal cord in the three fawns with paralysis. One white-tailed deer (Odocoileus virginianus) exposed to infective larvae from the same source survived infection without exhibiting clinical signs and began passing larvae in feces 88 days post-exposure. At the doses used in this study, meningeal worm caused fatal infections in fallow deer. Results are compared to published observations of fallow deer naturally-infected with P. tenuis.     

Evidence that size-selective mortality affects growth of Atlantic cod (Gadus morhua L.) in the southern Gulf of St Lawrence

The effects of size-selective fishing mortality on the growth of Atlantic cod ( Gadus morhuu L.) in the southern Gulf of St Lawrence were investigated and compared between: (1) a period when fishing mortality was relatively high, growth was relatively rapid, and abundance low (1967–1972 year classes): and (2) a period when fishing mortality was lower, growth was slow, and density high (1977–1982 year classes). Cod first entered the fishery at age 3 during both periods. The 1967–1972 year classes (fast growing) were fully recruited to the fishery by age 5 or 6 and the fishery removed over twice as many fish from the lower than upper quartiles of length-at-age distributions for cod 4 to 10 years old (disproportionately high exploitation of slow-growing fish). In contrast. the 1977–1982 year classes (slow growing) did not fully recruit to the fishery until age 9 or 10 and the fishery removed four times as many fish from the upper than lower quartiles of the length-at-age distributions for 4- to 10-year-old cod (disproportionately high exploitation of fast-growing fish). The reduced mean lengths-at-age of the 1977–1982 year classes compared with the 1967–I972 year-classes is consistent with the different patterns of exploitation of fast- and slow-growing fish for the two periods.     

Low-dose meningeal worm (Parelaphostrongylus tenuis) infections in moose (Alces alces)

Parelaphostrongylosis has a rapid onset and is lethal in neonatal moose (Alces alces) when large numbers of third-stage Parelaphostrongylus tenuis larvae (L3) are given experimentally. Little is known, however, about the severity and prognosis of infections acquired naturally by accidentally ingesting terrestrial gastropods which are rarely infected and have few larvae. To investigate the relationship between infecting dose, age of moose, and severity of disease, five calves were given low doses of three to 10 L3 when five (n = 2) or 9.5 mo old (n = 3). Each of two animals initially given low doses were later challenged with a dose of 15 L3. As positive controls, two calves were given doses of 15 and 30 L3, considered to be high. All five calves given low doses showed abnormal locomotory signs at 20-28 days postinoculation (DPI) that progressively became more pronounced with hind quarter weakness and front lameness. However, after 77-130 DPI, signs diminished markedly in two of these animals and disappeared in another two. Challenge infections of 15 L3 given 199 days after initial infections had no noticeable effects although an immature worm, probably resulting from the challenge, was found in the spinal cord of one animal killed 51 days later. Two positive control animals given the high doses of 15 and 30 L3 showed moderate to severe, non-resolving, locomotory signs and had to be euthanized. Results demonstrate that single, low doses of three to 10 P. tenuis L3 cause moderate disease in moose calves but over time, some worms die and animals can recover. A degree of protection may develop against future infection.     

Baseline responses of Alphitobius diaperinus (Coleoptera: Tenebrionidae) to cyfluthrin and detection of strong resistance in field populations in eastern Australia

Resistance to cyfluthrin in broiler farm populations of lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), in eastern Australia was suspected to have contributed to recent control failures. In 2000-2001, beetles from 11 broiler farms were tested for resistance by comparing them to an insecticide-susceptible reference population by using topical application. Resistance was detected in almost all beetle populations (up to 22 times the susceptible at the LC50), especially in southeastern Queensland where more cyfluthrin applications had been made. Two from outside southeastern Queensland were found to be susceptible. Dose-mortality data generated from the reference population over a range of cyfluthrin concentrations showed that 0.0007% cyfluthrin at a LC99.9 level could be used as a convenient dose to discriminate between susceptible and resistant populations. Using this discriminating concentration, from 2001 to 2005, the susceptibilities of 18 field populations were determined. Of these, 11 did not exhibit complete mortality at the discriminating concentration (mortality range 2.8-97.7%), and in general, cyfluthrin resistance was directly related to the numbers of cyfluthrin applications. As in the full study, populations outside of southeastern Queensland were found to have lower levels of resistance or were susceptible. One population from an intensively farmed broiler area in southeastern Queensland exhibited low mortality despite having no known exposure to cyfluthrin. Comparisons of LC50 values of three broiler populations and a susceptible population, collected in 2000 and 2001 and recollected in 2004 and 2005 indicated that values from the three broiler populations had increased over this time for all populations. The continued use of cyfluthrin for control of A. diaperinus in eastern Australia is currently under consideration.     

Effectiveness of treatment with antihypertensive drugs and trends in mortality from stroke in the community.

A study was made of the changes in the treatment of hypertension, in the effectiveness of that treatment, and in mortality from cerebrovascular stroke in men and women in two counties in Finland. One of these counties was North Karelia, where a comprehensive cardiovascular programme based in the community had been launched in 1972. Cross sectional surveys in large representative samples of the middle aged populations were carried out in 1972, 1977, and 1982. Average annual mortality from stroke adjusted for age was calculated for the two year periods 1971-2, 1977-8, and 1980-1. The proportion of hypertensive men being effectively treated for their hypertension increased in both areas from 1972 to 1977 and further from 1977 to 1982. Mortality from stroke in middle aged men decreased in both areas during both observation periods. The proportion of hypertensive women being effectively treated greatly increased in both areas from 1972 to 1977. This was associated with a large decline in mortality from stroke. In North Karelia the proportion of women being effectively treated was remarkably high but decreased somewhat between 1977 and 1982; this decrease was associated with an increase in mortality from stroke in the women aged 35-64. These results support the idea that effective antihypertensive treatment in the community is a major determinant of mortality from stroke in both men and women.     

The survival of Ostertagia circumcincta and Trichostrongylus colubriformis in faecal culture as a source of bias in apportioning egg counts to worm species.

When cultured alone or concurrently with Trichostrongylus colubriformis in sheep faeces, Ostertagia circumcincta produced fewer infective larvae per 100 eggs than did T. colubriformis. Averaged over five trials 60% of T. colubriformis eggs were recovered as infective larvae while for O. circumcincta the figure was only 39%. This result was observed for two strains of O. circumcincta and was independent of when larvae were harvested from culture (days 6-10 at 25 degrees C). The mortalities of both species occurred at the first and second larval stages. These observations are of concern when using larval differentiation from faecal culture to make quantitative estimates of worm egg numbers for each species present. Species such as T. colubriformis which have a low mortality during culture are likely to have their egg numbers overestimated when cultured with a species, like O. circumcincta, that suffers high mortality in culture.     

Population dynamics and epidemiology of Toxocara canis in Danish red foxes

Toxocara canis, an intestinal helminth of canids with zoonotic potential, was found in 618 (59%) of 1,040 red foxes (Vulpes vulpes) collected from all Danish provinces (1997-2002). The prevalence and average worm burden were significantly higher for cubs than older foxes and in males than in females. A multiple logistic regression demonstrated that the prevalence was influenced significantly by sex and age of foxes in addition to location, season, and year of collection. The highest prevalence and worm burden were found in rural areas. The size and number of female worms was positively correlated to the fecal egg excretion. The length and fecundity of the worms was significantly higher in male foxes, and a general intensity dependence was suggested from a negative correlation between worm numbers and worm lengths. As compared to intestinal recovery of worms, somatic larvae were recovered from 20% of muscle samples and fecal eggs in 41% of fecal samples. The consistent finding of T. canis larvae in somatic tissues of naturally infected foxes is new.