Spatio-temporal factors influencing the occurrence of Syngamus trachea within release pens in the South West of England

Syngamus trachea is a pathogenic tracheal nematode that causes syngamiasis in wild and game birds, especially when birds are managed at high densities. Despite its pathogenic nature, very little is known about its epidemiology and relationship with ambient temperature and humidity. The spatial and temporal modelling of disease was undertaken on two pheasant estates within the South West of England from April 2014 to August 2014. Significant differences between the mean numbers of eggs per gram of soil were identified between pens at both site 1 and site 2 but did not differ significantly between sites. Egg abundance was significantly associated with soil moisture content, with greater egg survival between years in pens with higher average volumetric soil moisture content. Previous years stocking density and pen age were also associated with greater egg survival between years with more eggs being recovered in pens with greater stocking densities, and pens that had been sited longer. The greatest model to explain the variation in the numbers of eggs per gram of soil per pen was a combination of soil moisture content, stocking density and pen age.Larval recovery differed significantly between sites. Larval abundance was significantly and positively associated with temperature and relative humidity at site 1. Similarly, temperature and humidity were also positively and significantly associated with larval abundance at site 2. Rainfall did not influence larval recovery at either site 1 or site 2. The model with the greatest ability to explain larval abundance at both sites, was a combination of temperature, humidity and rainfall. Infection status (positive faecal egg counts) was significantly and positively associated with larval abundance at both sites, but rainfall was only positively associated at site 1. Temperature and humidity were positively associated with infection status at site 2, but not at site 1. The present study highlights the influence of climatic variables on both egg survival and larval abundance, and could therefore be used to develop more targeted treatment strategies around periods of higher disease risk. The frequent use of release pens is a clear factor in the epidemiology of syngamiasis, and it is recommended that pens be rested and/or rotated in order to reduce infection pressure in subsequent flocks.     

Is the Santa Inês sheep a typical non-seasonal breeder in the Brazilian Southeast?

This study aimed to characterize the annual reproductive cycle of Santa Inês sheep in the Fluminense lowland region (latitude 22° 27′ 45″ south, Rio de Janeiro, Brazil) between September 2011 and August 2012. Ten ewes were maintained in a semi-intensive system under natural photoperiods with access to pasture and shelter. Blood samples were collected every 2 weeks to determine plasma progesterone concentrations. The body condition score (BCS) was determined each month. There was no seasonal variation in the plasma progesterone concentration from the months of September to January, April, and May to August. In the months of February and April, the plasma hormone levels were higher than August to November. Seventy percent (7/10) of the sheep studied had short seasonal anestrus. The periods of anestrus were concentrated between the months of September and December (spring season) in 85.7 % (6/7) of the cases evaluated. In these cases, 57.1 % (4/7) also had short periods of reproductive inactivity during other months of the year. The progesterone values obtained in the spring corroborate the higher reproductive anestrus observed in this season. Higher plasma progesterone values were found in summer and autumn with reduction in the winter to lower values in the spring. No changes in the BCS during the study period were observed. Under the studied conditions, the Santa Inês sheep showed a low degree of reproductive seasonality. However, some individual ewes had seasonal anestrus during the spring. Further studies that include management techniques are needed to improve reproductive efficiency without hormone therapy in this breed under tropical conditions.     

Oestrus ovis in sheep: relative third-instar populations, risks of infection and parasitic control.

Oestrus ovis (L.) (Diptera: Oestridae), the nasal bot fly, has a relatively short free-living life cycle outside of the host, and therefore it is necessary to know when the parasitic period occurs in order to prevent the clinical signs and economic losses caused by this parasite. The length of this parasitic portion of the life cycle is quite variable: a few weeks to several months depending on the season and climatic conditions. Surveys of Oestrus ovis larval populations in sheep show different results on the number of generations according to the local climate. Mean monthly larval profiles of L1 and L3 burdens of sheep from West African Sahelian countries, Mediterranean countries (Morocco, Tunisia and Sicily) and Southwest France were compared. Valuable information on the suspected extension of the fly season is obtained showing the period of infection in each area. This knowledge will be a valuable tool to help in choosing the right treatment at the right period.     

Development and survival of free-living stages of equine strongyles under laboratory conditions

In a series of laboratory studies the optimum conditions for the development and survival of the free-living stages of strongyle parasites occurring in horses in tropical north Queensland were determined. No differences in behaviour were noted between the strongyle species. Development to the infective stage occurred only between 10 and 35 degrees C. The rate was affected by temperature, taking 15-24 days and 3 days, respectively, at the lowest and highest temperatures for the developing stages to reach the infective third stage. Yields of infective larvae were very low outside the range 20-33 degrees C, and were highest at 28 degrees C. Survival of infective larvae was good between 20 and 33 degrees C, and large numbers were recovered after 3 months in faeces incubated at 20-28 degrees C. At 33 and 37 degrees C larval survival was affected by the moisture content of the faeces, with infective larvae surviving better in dry than in moist faeces; even a residual moisture level of 40% significantly reduced the number of larvae recovered from faeces incubated at 37 degrees C for 1 month. Moisture also affected larval development, especially at the higher temperatures of 25-39 degrees C. When faecal moisture content fell to less than or equal to 20% by 3 days, larvae which had not yet reached the infective stage were still pre-infective at 7 days, while all larvae in faeces with adequate moisture had reached the infective third stage. It was not possible to determine the critical faecal moisture level below which larval development ceased, however, 28 degrees C (range 25-33 degrees C) was found to be the optimum temperature. Larval development was very rapid and yields of infective larvae highest at this temperature.     

Reproductive cycle of the Namib giant ground gecko,Chondrodactylus angulifer (Squamata: Gekkonidae)

The reproductive cycle of the Namib giant ground gecko, Chondrodactylus angulifer, from southern Africa was described from a histological examination of gonadal material from museum specimens. Males followed a seasonal testicular cycle in which (based on available specimens) the major period of spermiogenesis occurred between September and December. The onset of spermiogenesis is not known as specimens from May to August were not available. Testes in regression were found in January, February and March. Testes in recrudescence were found in January, February, March and April. Females with enlarged ovarian follicles (>5mm length) were found in January/February and September to December. Mean clutch size for 36 females was 1.7 ± 0.47 S.D., range: 1–2. Evidence is presented that more than one clutch may be produced in the same reproductive season.     

Further evidence on the internal life cycle of Przhevalskiana silenus (Diptera, Oestridae)

Knowledge of the internal life cycle of goat warble fly infestation is scarce despite ample data available on the aetiology, epidemiology, immunodiagnosis and treatment of such infestations. This study was carried out at the slaughterhouse of Rossano Calabro (Cosenza, southern Italy) on 154 animals from 10 months to 6 years of age from May 1997 to June 1998. 1206 Przhevalskiana silenus larvae were collected during the trial period from the subcutaneous tissue of the slaughtered animals. The larval stage average size ranged from 4.7 mm, for first instar larvae (May), to 16.6 mm, for third instar larvae (February), in the first cycle of infestation. No larvae were found in March-April, coinciding with the pupation period. Small first instar larvae were found at the beginning of the second cycle of infestation (May-June). Necroscopic examinations were also carried out on internal organs and no larvae were found. The results pointed out that the internal life cycle of P. silenus is exclusively subcutaneous and there is no internal migration of the larvae.     

Endocrine and testicular changes associated with season, artificial photoperiod, and the peri-pubertal period in stallions.

The seasonal reproductive cycle of stallions is characterized by an annual regression and recrudescence in testicular function and concentrations of LH, FSH, and testosterone in serum. Maximum reproductive capacity occurs during the increasing day lengths of spring and summer. The annual cycle in LH secretion may reflect a seasonally associated and photosensitive reduction and replenishment in pituitary content of LH. Similar to other seasonal breeders, it appears that stallions may possess an endogenous circannual rhythm in reproductive function that is subject to manipulation by altering the light:dark ratio, i.e., photoperiod. The application of a long-day photoperiod (16 hours light:8 hours dark) in December, following 20 weeks of short days (8 hours light:16 hours dark), was effective in hastening the seasonal sexual recrudescence of stallions but was not effective in prolonging the interval of heightened reproductive capacity. The infantile period in colts lasts approximately 32 weeks and is characterized by low gonadotropin concentrations and little gonadal activity. The start of the pre-pubertal period is marked by changes in the hypothalamic-pituitary axis which result in increased amounts of LH and FSH secretion between 32 and 40 weeks of age. Testosterone concentrations in serum exhibit a dramatic increase at 75 to 80 weeks of age, with puberty (defined as the age when the first ejaculate was obtained containing a minimum of 50 x 10(6) sperm with greater than or equal to 10% progressive motility) occurring at 83 weeks of age.     

Observations on the population dynamics of five cyathostome nematode species of horses in northern USA

Monthly variations in the magnitude of adult and larval cyathostome burdens were observed in 55 horses necropsied over a 15-month period in the northern USA. Peak numbers of adult cyathostomes occurred in late winter (March) and late summer (September). Larval cyathostomes demonstrated peak numbers from February to April and again in October, beginning one month earlier than the spring adult peak and one month after the autumn adult peak, respectively. The reproductive status of individual female Cyathostomum catinatum, Cyath coronatum, Cylicocyclus nassatus, Cylicostephanus goldi and Cylicostephanus longibursatus was classified as immature, gravid or spent. Seasonal changes in these classifications were monitored as a marker for the age structure of these populations. Each reproductive category of female small strongyle was dominant during only one period per year and these periods were similarly distributed for all five species examined. Immature cyathostomes were most common from late winter to spring (March to May); gravid worms were predominant beginning in spring (April/May) and continuing into autumn (October to December). Spent females prevailed from autumn through winter (October to March/April).     

Mechanisms of survival of nematode parasites with emphasis on hypobiosis

Mechanisms involved in parasitic nematode survival must be considered with reference to their host and environmental interrelationships since these interrelationhips ultimately influence any parasite adaptations aimed at survival.The most important of the potential environmental constraints are climatic, particularly temperature and humidity, and these can drastically influence larval development and survival.One of the major host factors influencing successful parasite survival is the availability of suitable (susceptible) new hosts to the infective stages of the parasite at the appropriate time for transmission to be achieved. Other host factors that influence parasite survival are those that affect the entrance, establishment and reproduction of the parasite within its new host; mainly problems of acclimatization to a parasitic way of life as well as the countering or adaptation to a variety of host resistance factors, both molecular and cellular, by the parasite.Finally in order for life cycles to be completed, the parasite must evolve means whereby its larval forms can leave the host so that eventual transmission to a new host can be accomplished.In this paper a number of adaptations which enable the parasite to overcome these constraints are discussed. These include such things as larval resistance to environmental effects, the utilization of intermediate hosts or vectors for transmission, seasonally-increased fecundity rates, anti-host immunity stratagems and hypobiosis.This latter phenomenon, hypobiosis or prolonged but temporarily arrested larval development, represents one of the most useful of life cycle adaptations to ensure parasite adaption enables the parasite to synchronize its life cycle to changing environmental or survival and appears to be widespread among parasitic nematodes. Among its benefits, this host conditions. It can thus be of major importance in ensuring survival of the parasite during periods of environmental adversity when conditions for transmission are poor and survival of free-living forms may be minimal. It also enables the parasite to have available large numbers of infective forms at points in the host reproductive cycle which coincide with the production of the susceptible neonates thereby greatly facilitating transmission. Additionally, with certain species of nematodes, occurring as it does at times of the year when the numbers of infective stages may be high while host resources may be limited, oscillations in parasite biomass can be avoided. It thus serves as a highly adaptive mechanism for regulating populations of adult worms, lessening stress on the host and favoring parasite survival as a result.     

Changes in the concentrations of serum IgG, IgA and IgM of sows throughout the reproductive cycle

The concentrations of IgG, IgM and IgA in sera collected from 3855 sows (3208 pregnant and 647 lactating) at a single time point were determined. This experimental design allowed changes in serum immunoglobulin over the reproductive cycle to be studied without bias from seasonal influence. The concentrations of the three immunoglobulins changed independently during the reproductive cycle. Serum levels of IgM and IgG began a progressive postpartal decline during the 14th–17th week of gestation. At the onset of lactation serum IgG levels progressively increased while IgM levels continued to decline, the latter reaching their lowest level during the third week of lactation. In contrast to IgM and IgG, serum IgA levels increased 35% during weeks 14–17 of gestation and continued to increase throughout lactation, reaching their highest serum levels in the third week of lactation; the serum IgA concentration at this time was twice that observed during the first 13 weeks of gestation. Results of these studies allowed the reproductive cycle to be classified into four phases on the basis of serum immunoglobulin concentrations: (1) weeks 1–4 of gestation; (2) weeks 5–13 of gestation; (3) weeks 14–17 of gestation and (4) lactation.     

Development and survival of Haemonchus contortus larvae on pasture at Vom,Plateau State,Nigeria

The development and survival of the eggs of Haemonchus contortus on pasture at Vom were studied by depositing faecal pellets on grass plots over a period of 12 months. Development and survival to the infective larvae occurred throughout the study except during the dry season months of December to April. More infective larvae were recovered from the herbage in June, July and August than in other months. The survival time of the infective larvae ranged from 2 weeks in October to 10 weeks in June, July and August. Rainfall was the most important epizootiological factor influencing the development and survival of the infective larvae. Temperature was not a limiting factor.     

Further studies on the development and availability of infective larvae of bovine gastrointestinal trichostrongylids on pasture in eastern Nigeria

The dynamics of pasture populations of infective larvae (L3) of Cooperia, Haemonchus and Trichostrongylus species were studied at Nsukka, eastern Nigeria, during April to November 1984. Six paddocks were contaminated artificially and one was contaminated naturally. Five of the paddocks, P1-P5, were sequentially contaminated with faeces of naturally infected cattle at approximately 4-6-weekly intervals. Paddocks P6 and P7 were repeatedly contaminated every 4-6 weeks artificially and by the naturally infected cattle, respectively. Larval development and survival occurred very readily during the wet season (April-October) but apparently ceased in November at the start of the dry season. Larval migration, however, occurred not only during the rains but also during the first 4 weeks of the dry season. Single contaminations during the rains quickly gave rise to single waves of infestation which also declined rapidly, in spite of the continuously favourable conditions for larval development and survival. The repeated contaminations produced three and four distinct and relatively short-lived larval peaks, respectively, with the first three peaks on both paddocks, namely the May, July and September/October peaks, being coincident. The four waves of herbage infestation on P7, which occurred at approximately 4-5 weekly intervals, were considered to have originated from four separate generations of the three trichostrongylids. However, Trichostrongylus sp. predominated in the first (May) peak while Cooperia and Haemonchus dominated the later peaks.     

The Female Reproductive Cycle of the Neotropical Snake Atractus pantostictus (Fernandes and Puorto, 1993) from South‐eastern Brazil

Data on reproductive activity of fossorial species are limited because the specimens are difficult to be observed and captured. Here in, we present the reproductive cycle of female Atractus pantostictus, a fossorial neotropical species, and the sexual maturity of males and females in south‐eastern Brazil. The female reproductive cycle of A. pantostictus is seasonal, with vitellogenic follicles being found from September to April and eggs in November, February, March and April with the number varying between two and four. Spermatozoa were found in the lumen of the glandular and non‐glandular uterus in females collected during the rainy season. Sperm storage tubules were found in the posterior infundibulum of the females, where the storage of sperm occurs for a short time. The storage may occur because mating and ovulation are dissociated.     

Seasonal translation of equine strongyle infective larvae to herbage in tropical Australia

Longevity in faeces, migration to and survival on herbage of mixed strongyle infective larvae (approximately 70% cyathostomes: 30% large strongyles) from experimentally deposited horse faeces was studied in the dry tropical region of North Queensland for up to 2 years. Larvae were recovered from faeces deposited during hot dry weather for a maximum of 12 weeks, up to 32 weeks in cool conditions, but less than 8 weeks in hot wet summer. Translation to herbage was mainly limited to the hot wet season (December-March), except when unseasonal winter rainfall of 40-50 mm per month in July and August allowed some additional migration. Survival on pasture was estimated at 2-4 weeks in the summer wet season and 8-12 weeks in the autumn-winter dry season (April-August). Hot dry spring weather (pre-wet season) was the most unfavourable for larval development, migration and survival. Peak counts of up to 60,000 larvae kg-1 dry herbage were recorded. The seasonal nature of pasture contamination allowed the development of rational anthelmintic control programs based on larval ecology.     

Changes in concentrations of plasma immunoreactive follicle-stimulating hormone, luteinizing hormone, estradiol-17beta, testosterone, progesterone, and inhibin in heifers from birth to puberty

This study was designed to clarify the characteristics of changes in plasma concentrations of reproductive hormones in heifers from birth to puberty. Weekly or daily hormonal changes were observed in 39 heifers. Daily changes in the concentration of follicle-stimulating hormone (FSH) demonstrated a consistent cycle of hormone changes over a 7- to 8-day period in heifers from approximately 10 days to 9 months old. Weekly changes in reproductive hormones showed that there were three brief periods in heifers between birth and puberty in which dramatic changes occur. The first period was the first week after birth, during which a reciprocal relationship between steroid hormones and gonadotropins was observed. At birth, the concentrations of steroid hormones were higher than those at any other age. These hormone levels rapidly decreased within the first week after birth. Gonadotropin levels, however, increased from birth to 1 week of age. The second period of major change was at approximately 4 weeks of age when there was an increase in the concentrations of luteinizing hormone (LH), estradiol-17beta, testosterone, and immunoreactive inhibin. The third period was the last 5 weeks before the first ovulation, when there was an increase in the concentrations of estradiol-17beta followed by an increase in (LH). These results suggest that regular hormone changes start from 10 days after birth and that the periods from birth to 4 weeks of age and the last 5 weeks before the first ovulation in heifers are important to the development of reproductive functions before puberty.     

湖南省黄鳝源胃瘤线虫生物学特性研究

胃瘤线虫病是一种由寄生于鱼类、鸟类体内的线虫引起的疾病,对野生动物保护、养殖业均构成较大威胁。试验于2012年4月-2013年4月用蠕虫学剖检方法检查了58839副黄鳝内脏胃瘤线虫的感染情况,并对其感染平均丰度、虫体长度、体长与存活时间关系进行观察与分析,同时测定了黄鳝血液pH。结果显示,胃瘤线虫的平均丰度为5.45%,其中春夏季平均丰度（7.85%）大于秋冬季平均丰度（4.08%）,野生黄鳝平均丰度（4.08%）明显高于养殖黄鳝平均丰度（1.10%）,表明胃瘤线虫平均丰度受季节及养殖方式的影响;测量300条胃瘤线虫平均长度为49.69 mm(体长范围为26.80～70.50 mm),春夏季及秋冬季虫体平均长度分别为47.10、54.86 mm,表明胃瘤线虫秋冬季长度整体长于春夏季;虫体长度在＜30、30～39.9、40～49.9、50～59.9、＞60 mm的平均存活时间分别为2.5、3.6、4.4、5.4、9.0 d,表明虫体存活时间与虫体长度呈一定的正相关;黄鳝血液pH无明显季节性变化。本试验结果可为湖南省胃瘤线虫病防制提供依据。     

The biology of Ctenocephalides canis in Ireland.

A colony of Ctenocephalides canis was established using dogs as hosts. Two diets were used as media. Fleas reared on cats did not develop beyond the first larval stages. The effects of different temperatures on egg hatching and larval development were examined. Larval survival was poor at 22 degrees C and 25 degrees C at 50% relative humidity, but good at 75% relative humidity at these temperatures. The development from egg to adult took 21 days.     

Survival of larvae of Boophilus annulatus, Boophilus microplus, and Boophilus hybrids (Acari: Ixodidae) in different temperature and humidity regimes in the laboratory.

The survival period for larvae of Boophilus annulatus (Say), Boophilus microplus (Canestrini) and hybridized Boophilus ticks was determined by exposure to various combinations of temperature (20, 25, 30 and 35°C) and relative humidity (32, 63, 75, 84 and 97% RH) in the laboratory. Results indicated that within a given temperature and RH regime, there was no difference (P> 0.05) in larval survival among the three species tested, indicating that these ticks respond similarly over a wide range of temperature and RH combinations. Larval survival in all three species was longest (P < 0.05) at 20°C and either 84 or 97% RH. With each increase in temperature at the 84 and 97% RH treatment levels, there was a corresponding significant (P < 0.05) decrease in larval survival. When the temperature reached 35°C at all humidities or when the RH was 63% or less at all temperatures, the mean larval survival period was 43 days or less in all cases and little difference (P> 0.05) was observed among the treatment regimes included. Results suggest that at a RH of 75% and more, the temperature is the determining factor in larval survival, whereas at a RH of 63% and less the RH is the determining factor in larval survival, regardless of temperature.