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1.
An outbreak of foot lameness in a dairy herd of 170 goats is described. The herd, that was kept mostly indoors, was attended between December 2006 and November 2007. During this period, 15% of the goats showed lameness with foot lesions and 24% of the goats showed lameness without foot lesions. The foot lesions consisted of cracks and erosions on the horn of the bulbs of the heel that in most cases extended along the internal side of the axial hoof wall. The clinical diagnosis was interdigital dermatitis. Annual milk production was lower in lame goats compared to those that were not lame (P < 0.05). Furthermore, annual milk yield was significantly affected by the type of foot disease present and was significantly lower in cases with foot lesions than in the animals that were not lame (P < 0.05) and also in the lame goats without foot lesions (P < 0.05).  相似文献   

2.
Sow lameness can result in decreased animal health and productivity, and is a significant animal welfare concern. Swine producers and veterinarians lack objective assessment tools to detect lameness. Objectives of this study were to evaluate pressure algometry (PA) and thermal sensitivity (TS) as objective assessment tools for changes in pain sensitivity associated with lameness and to assess analgesic drugs for mitigating lameness pain. Twelve mixed parity crossbred sows were anesthetized and injected with Amphotericin B in the distal interdigital space of both claws of one hind leg to induce transient lameness. Sows were randomly assigned to one of three analgesic treatment groups: (1) Sodium Salicylate (SS; 35 mg/kg per os q.12 h+0.04 ml/kg IM q.24 h sterile saline), (2) Flunixin meglumine (FM; 2.2 mg/kg IM q.24 h), or (3) Control (C; 0.04 ml/kg IM q.24 h sterile saline). All sows received each treatment over three trials with two-wk wash-out periods between trials. Forty-eight h post-induction, analgesic treatments were administered daily for four consecutive d. Pain sensitivity was assessed with PA and TS on each hind leg on d−1, d+1 and d+6 relative to induction (d0). Proc Glimmix of SAS 9.2 was used to analyze the difference between sound (S) and lame (L) legs on each trial day, with a simple effect comparison used to analyze effect of analgesia treatment on d+6. As predicted, S and L legs did not differ on d−1 (P=0.56) and less pressure was tolerated on L legs on d+1 (P<0.001) (Raw Means in kilograms of force: d−1 L 7.2±0.2; d−1 S 7.4±0.2; d+1 L 2.1±0.2; d+1 S 7.7±0.2 kgf). A simple effect comparison of d+6 revealed no differences between FM and C (p=0.90), FM and SS (p=0.17), or SS and C (p=0.07). The TS latency of S versus L legs differed on all trial days (d−1 p=0.02, d+1 p<0.0001, d+6 p<0.01) over all trials. (TS Raw means (s): d−1 L 7.3±0.6; d−1 S 9.1±0.6; d+1 L 3.3±0.2; d+1 S 6.8±0.6; d+6 L 6.0±0.6; d+6 S 8.4±0.7 s), including lame and sound days. In conclusion, these results support PA as an objective non-invasive method for measuring pain sensitivity in sows induced with transient lameness. Sodium salicylate or flunixin meglumine did not reduced pain sensitivity as measured by PA from d+1 to d+6 in this model of induced transient lameness.  相似文献   

3.
Mycoplasma suis, the causative agent of porcine infectious anemia, causes large economic losses to the swine industry worldwide. A questionnaire-based survey was conducted in 69 pig farms in Hubei Province, China, from November 2011 to August 2013 to ascertain the prevalence and associated risk factors of M. suis. Four thousand and four blood samples from pigs of all the age groups were tested for M. suis antibodies using the established rMSG1–ELISA assay. Among these 4004 samples, 1615 blood samples from multiparous sows were examined to identify the association between seroprevalence and different seasons. Information on risk factors collected from farmers or attending veterinarians was recorded on a pre-designed questionnaire. The overall test seroprevalence of M. suis infection at the animal level was 31.9% (1277/4004; 95% CI: 30.5%, 33.4%), whereas at the farm level, this value was 95.65% (66/69; 95% CI: 87.8%, 99.1%). The seroprevalence of M. suis was higher in replacement gilts (40.6%; 95% CI: 35.1%, 46.3%), multiparous sows (48.2%; 95% CI: 45.8%, 50.7%) and boars (44.4%; 95% CI: 34.5%, 54.8%), as compared to piglets (13.0%; 95% CI: 9.4%, 17.3%), weaned-piglets (10.8%; 95% CI: 8.9%, 13.0%), and growing-finishing pigs (25.0%; 95% CI: 22.0%, 28.3%). In terms of seasons, the prevalence of M. suis in pigs was significantly higher in summer (65.3%; 95% CI: 61.0%, 69.5%) and autumn (65.0%; 95% CI: 59.0%, 70.6%) compared to spring (30.1%; 95% CI: 26.0%, 34.4%) and winter (36.4%; 95% CI: 31.4%, 41.5%). Farm-level risk factors were identified by multivariable logistic regression analysis. The associated factors retained in the final multivariable logistic regression model were drug treatment, presence of mosquitoes and flies, and frequency of disinfection. Drug treatment (OR = 0.24; 95% CI: 0.07, 0.88; P = 0.031) and frequency of disinfection (OR = 0.23; 95% CI: 0.06, 0.90; P = 0.035) were protective factors, and the presence of mosquitoes and flies (OR = 5.994; 95% CI: 1.56, 23.00; P = 0.009) was a risk factor for M. suis infection on farms. The results of the present study provide the first insight into the impact of associated determinants on M. suis infection in central China.  相似文献   

4.
The aim of the present study was to evaluate anti-Neospora caninum antibodies and the vertical transmission rate in naturally infected pregnant zebu beef cows (Bos indicus) reared on pasture. The present study began with 200 cows from four farms (50 cows from each farm), and these animals were submitted to timed artificial insemination (TAI). After ultrasonography, 76 pregnant cows were selected, 22, 15, 22, and 17, respectively, from farms 1, 2, 3, and 4. Blood samples were taken from cows thrice during the first, second, and third trimester of gestation, and a blood sample was collected from 31 calves before colostrum milking. From 76 cows 23 (30.3%) had anti-N. caninum antibodies detected by indirect ELISA (Idexx), and 53 (69.7%) did not. Sixty-four cows that initiated the experiment were negative to N. caninum and 11 became positive either during the second or third trimester of gestation, this mean an infection incidence of 17.2% (11/64). OD for ELISA was higher (OD = 2.08) during the second and third (OD = 2.10) trimesters of pregnancy when compared with the first (OD = 1.81), however, there were no statistical differences (P = 0.45). The vertical transmission was calculated to be 29.0% (9/31), and the risk of vertical transmission of N. caninum in seropositive dams was 26.25 times higher than seronegative animals (OR = 26.25, 2.38 < OR < 289, P = 0.007). In conclusion, the rate of vertical transmission of N. caninum in pregnant zebu beef cows was 29%, and the risk was 26.25 higher in seropositive dams relative to than seronegative animals.  相似文献   

5.
N and P surpluses per hectare at farm level were determined on 63 private pilot farms with data from 2 to 7 years between 1997 and 2003 (a total of 245 observations). Farms were classified in the following four farm types: Conventional mixed dairy, organic mixed dairy, conventional pig farms (indoor) and conventional pig farms with outdoor sows. Import of nutrients with concentrate and fertilizer was the major input to all conventional farm types. On the organic dairy farms major input was N fixation, but also import of nutrients with concentrate and manure were important inputs. Output from the dairy farms was dominated by nutrients in milk. On pig farms nutrients in meat dominated the output, but also export of nutrients with cash crops and manure were important outputs. Farm type, year and farm within farm type significantly affected both N and P surpluses per hectare. Farm type was the major source of variation in both N and P surpluses. In the period investigated N surplus decreased by 6.5 kg N ha− 1 yr− 1 and P surplus decreased by 0.7 kg P ha− 1 yr− 1. The N and P surpluses observed on the conventional dairy farms significantly exceeded surpluses observed on the organic dairy farms. At equal number of livestock units (LU) per hectare (1.28 LU ha− 1) the difference was 43 kg N ha− 1 and 6 kg P ha− 1. At equal rates of N or P in manure to fields (147 kg N ha− 1, 29 kg P ha− 1, respectively) the difference was 45 kg N ha− 1 and 4 kg P ha− 1. Conventional dairy farms and pig farms with sows indoors had equal N and P surpluses at equal rates of N or P in manure to fields. Corrected to the average year (1999.5) the estimated average N and P surpluses showed highest levels on pig farms with outdoor sows (251 kg N ha− 1, 42 kg P ha− 1) and lowest levels on organic dairy farms (113 kg N ha− 1, 7 kg P ha− 1). Surpluses on the conventional dairy farms were 175 kg N ha− 1 and 16 kg P ha− 1 and on the indoor pig farms they were 123 kg N ha− 1 and 13 kg P ha− 1. The N and P surpluses observed on Danish conventional mixed dairy farms were comparable with intensive dairy farming systems in other European countries.  相似文献   

6.

Background

The effects of lameness on fertility have been documented frequently but few data are available from seasonally breeding, pasture-based herds (such as those used in Ireland) where cows are housed during the winter months but managed at pasture for the remainder of the year. This study determined the prevalence of lameness in a group of 786 cows in 10 pasture-based Irish dairy herds before, during and after the breeding season and assessed the relationship between lameness and the reproductive performance in these herds through serial locomotion scoring during the grazing period.

Results

Lameness prevalences of 11.6 % before, 14.6 % during and 11.6 % after the breeding season were found and these compared favourably to results from housed cattle and are similar to other studies carried out in grazing herds. A Cox proportional hazards model with locomotion score as time varying covariate was used. After controlling for the effect of farm, month of calving, body condition score at calving, body condition score loss after calving and economic breeding index, cows identified as lame during the study were less likely to become pregnant. Cows lame before the earliest serve date but no longer lame during the breeding season, cows becoming lame after the earliest serve date and cows identified lame both before and after this date were respectively 12 %, 35 % and 38 % less likely to become pregnant compared to cows never observed lame during the study. However, these findings were only significant for cows becoming lame after the earliest serve date and cows lame both before and after the start of breeding.

Conclusions

This study found that the reproductive efficiency was significantly (p < 0.05) lower in cows becoming lame during the breeding season and cows lame before and during the breeding season compared to non-lame cows. Cows no longer lame during the breeding season had a lower Submission Rate to first serve within 3 weeks of earliest serve date. However, the Pregnancy Rate was not significantly (p > 0.05) lower in these animals compared to cows never diagnosed as lame. In addition to lameness status, nutritional status and genetics were found to influence the reproductive performance in pasture-based Irish dairy herds.  相似文献   

7.
A seroepidemiological survey of bovine leukemia virus (BLV) infection was conducted in Japan in 2007 using an enzyme-linked immunosorbent assay (ELISA) and an agar gel immunodiffusion (AGID) test. A total of 5420 cattle (dairy, 3966; breeding beef, 797; fattening beef, 657) from 209 farms in seven prefectures in Japan were tested. The overall prevalence of BLV infection was 28.6%. The prevalence of BLV infection in dairy cattle (34.7%) was higher than for both fattening beef cattle (7.9%) and breeding beef cattle (16.3%). Age-specific prevalence showed that BLV prevalence increased with age in all types of cattle and was notably different between dairy and beef cattle under 1 year of age. Among 207 farms, 141 herds (68.1%) had one or more positive animals. The proportion of these positive farms was significantly higher among dairy farms (79.1%) than among beef breeding farms (39.5%) and beef fattening farms (51.9%) (P < 0.001). Dairy farms (40.5%) also showed a significantly higher within-herd prevalence than beef breeding (27.4%) and fattening (14.9%) farms (P = 0.001). This study indicated that BLV is more widely spread in dairy cattle than in beef breeding cattle in Japan. Given the prevalence of BLV infection in dairy and beef cattle was 8- and 1.7-fold higher, respectively, than rates previously found in 1980–1982, BLV appears to be spreading particularly among the dairy cattle population during the last two decades. Further investigation is required to determine the risk factors necessary to control BLV infection that take into account the different farming practices that exist between dairy and beef sectors.  相似文献   

8.
Neosporosis is considered to be a contributing risk factor for abortions in dairy cows and other farm animals and has negative economic impact on their breeding. In respect of the rapid spread of neosporosis in herds throughout the world, our aim was to detect the prevalence of anti-Neospora antibodies in cows post-abortion (PA) (PA Group n = 716) and in cows without any reproduction problems (Control Group n = 247) on large breeding farms from Eastern Slovakia. The overall mean seropositivity in PA Group (20.1%) was significantly higher (p < 0.0001) in comparison with the Control Group (2.3%), and this demonstrates the causal dependency of abortions on neosporosis. On farms from south-east region, 15.6% of cows were seropositive on average ranging from 7.8% to 25.8% in different districts. In the northern region, significantly (p = 0.0002) higher 26.2% mean seropositivity was detected. The seroprevalence in different districts ranged from 2.9% to 39.4%. In the PA Group a high seropositivity to infectious bovine rhinotracheitis (41.5%) and sporadic occurrence of Q-fever, leptospirosis and chlamydiosis was also detected. From 11 Toxoplasma-seropositive cows, only one animal was simultaneously positive to Neospora. The relatively high prevalence rate in cows warrants the attention and a need of surveillance in Slovak herds. A better knowledge of epidemiology of this etiological agent and the mechanisms of its transmission may help in the introduction of more effective preventive and control measures.  相似文献   

9.
To counteract the effects of perinatal hypoxia in piglets, the oral administration of caffeine to sows with induced parturition was evaluated. On day 113 of gestation 9 sows received 27 mg/kg body weight (BW) of caffeine mixed with 200 g of standard diet. The same amount of feed without the addition of caffeine was administered to 9 control sows. Additionally, on day 113 of gestation, all sows were treated by two injections in the perianal area of 1 mg of alfaprostol (at 8:00 am and 14:00 pm), and on the morning of farrowing by 14 IU of oxytocin in the perianal area. Caffeine did not affect BW of piglets and size of litters; however piglets from treated sows showed a higher capacity to adapt to extra-uterine life. Particularly, they showed a greater thermoregulatory ability (P<0.001) and a higher percentage of viability score≥7 compared to piglets from control sows (92% vs. 75%, respectively; P=0.030). Caffeine furthermore reduced the frequency of high serum biopterin values (>80 nmol/L) in piglets born from treated sows (P=0.001). In conclusion, the caffeine orally administered to sows with induced parturition showed a protective effect on the consequences of neonatal hypoxia in tissue ischemia–reperfusion injury in piglets.  相似文献   

10.
Frequency of removal reasons of sows in Southeastern Mexico   总被引：1，自引：1，他引：0  
  相似文献   

11.
The effects of floor heating at parturition on sow and piglet behaviour in pens were examined in a Danish production herd. A total of 50 gilts and sows were split into two groups; one (n = 25) experienced no treatment; one (n = 25) was exposed to floor heating in the area of the sow around parturition. The sows and piglets were recorded on video 24 h a day for behavioural analyses.Floor heating tended to improve piglet weight at weaning (P = 0.05) but did not affect average daily gain. Piglets in pens with floor heating were more often in proximity of the sow at posture changes than piglets from pens without floor heating on day one postpartum (P = 0.01). Floor heating did not affect duration of parturition or any of the recordings of sow behaviour significantly.  相似文献   

12.
During a 12-month period lameness, claw lesions and claw infections were studied in 15 herds with loose housing of pregnant sows on partly slatted concrete floors. Of these herds, 12 herds had concrete slats and 3 herds had plastic slats. The mean prevalence proportion of lame sows in the herds was 13.1%. The risk of lameness increased with increasing claw lesion score and with the presence of claw infections. In the herds with concrete slats, the relative risk of lame sows was 2.4 times higher than in the herds with plastic slats. In the herds with poor floor hygiene, the relative risk of lameness was 2.8 times higher than in the herds with dry and clean floors. The mean prevalence proportion of sows with claw infections at the 3 separate examinations in the 15 herds was 3.8%. Claw infections were more prevalent in herds with dirty floors and in herds with little space per animal (<2m2). In the herds with concrete slats, the relative risk of claw infections was 2 times higher than in the herds with plastic slats.  相似文献   

13.
The objective of this study was to evaluate the prevalence of infection with porcine circovirus-2 (PCV-2) and porcine reproductive and respiratory syndrome virus (PRRSV) through a longitudinal study in an integrated swine production system (7 farms) experiencing postweaning multisystemic wasting syndrome (PMWS). Risk factors for PCV-2 infection and for PCV-2 and PRRSV coinfection were also evaluated. Fifteen sows from each herd and 4 non-cross-fostered piglets from each sow were randomly selected at farrowing and ear-tagged at birth. Serum samples were analyzed for antibodies to PCV-2 and for detection of the PCV-2 and PRRSV genomes. Statistical analyses involved 2 approaches. The 1st approach characterized the dynamics of PCV-2 infection and their relationship with PRRSV infection. The 2nd approach analyzed the probability of being infected by PCV-2 or by both PCV-2 and PRRSV through a generalized linear mixed model incorporating sow and farm characteristics. At the 1st sampling time (1 wk of age), there was a significant relationship between sow PCV-2 infection and piglet PCV-2 infection (P < 0.0001). The risk of PCV-2 and PRRSV coinfection was 1.85 times greater in piglets from a sow with low titers of PCV-2 antibodies than in piglets from sows with medium to high titers (P = 0.03) and was 2.54, 2.40, and 2.02 times greater, respectively, in piglets from primiparous sows, PCV-2-infected sows, and farms in an area of high pig density than in piglets from sows of higher parity (P = 0.004), noninfected sows (P = 0.04), and farms in a low-density area (P = 0.09).  相似文献   

14.
The present study was conducted to evaluate non-return rate (NR), farrowing rate (FR), and number of total pigs born/litter (TB) of weaned sows after intra-uterine insemination (IUI) using low numbers of frozen–thawed (FT) spermatozoa. Semen from 6 boars was cryopreserved individually in a 0.5-ml straw, at a concentration of 1 × 109 spermatozoa/ml. A total of 40 multiparous sows with weaning-to-estrus interval of 3 to 7 days were included. The sows were detected for standing estrus twice daily and randomly assigned to two groups: I) spontaneous ovulation (n = 20) and II) induced ovulation (n = 20) which the sows were given 750 IU human chorionic gonadotrophin (hCG) i.m. immediately at estrus detection. Ovulation was determined every 12 h using transrectal ultrasonography. FT semen containing 1 × 109 motile spermatozoa/dose was used to IUI. In group I, the sows were inseminated at 24 h after the detection of estrus and repeated every 12 h until ovulation. In group II, the sows were inseminated at 36, 42 and/or 48 h after hCG treatment. The results showed that the interval from standing estrus to ovulation (EOI) differed significantly between group I (40.2 h) and group II (35.6 h; P = 0.01). Variation of EOI among sows within each group seemed to be lower in group II (4.5 h SD) than in group I (5.5 h SD; P = 0.5). The number of IUI per sow was 2.9 ± 0.6 times in group I and was 2.4 ± 0.5 times in group II. There were no significant differences (P > 0.05) in the NR (80 vs 85%), FR (60 vs 65%) and the TB (8.0 ± 2.8 vs 9.4 ± 3.7 piglets/litter) between the groups. These results indicated that multiple doses of IUI with a low number of FT boar spermatozoa provided a fairly good NR, and reasonable FR and TB both in spontaneous and induced ovulating sows. The number of inseminations required for attaining acceptable fertility tended to be lower in the weaned sows with induced ovulation.  相似文献   

15.

Background

Avian influenza is a severe threat both to humans and poultry, but so far, no systematic review on the identification and evaluation of the risk factors of avian influenza infection has been published. The objective of this meta-analysis is to provide evidence for decision-making and further research on AI prevention through identifying the risk factors associated with AI infection on poultry farms.

Methods

The results from 15 selected studies on risk factors for AI infections on poultry farms were analyzed quantitatively by meta-analysis.

Results

Open water source (OR = 2.89), infections on nearby farms (OR = 4.54), other livestock (OR = 1.90) and disinfection of farm (OR = 0.54) have significant association with AI infection on poultry farms. The subgroup analysis results indicate that there exist different risk factors for AI infections in different types of farms.

Conclusions

The main risk factors for AI infection in poultry farms are environmental conditions (open water source, infections on nearby farms), keeping other livestock on the same farm and no disinfection of the farm.  相似文献   

16.
Despite cattle herds can harbor Coxiella burnetii, risk factors for C. burnetii presence in dairy cattle herds are largely unknown. Therefore, C. burnetii herd prevalence and risk factors for bulk tank milk (BTM) positivity were investigated. In this cross-sectional study, a questionnaire was filled out by the farmer and BTM from 301 farms was tested by ELISA for presence of C. burnetii antibodies and PCR for presence of C. burnetii DNA. Risk factors were identified by univariable and multivariable logistic regression analyses. Antibodies to C. burnetii were detected in 81.6% (CI: 77.2–85.9) and C. burnetii DNA in 18.8% (CI: 14.4–23.1) of the BTM samples. Herd size (OR = 1.1 per 10 cows), cleaning the bedding of the cubicles at most every other day (OR = 2.8) and purchase of cattle from at least two addresses (OR = 3.1) showed a significant and positive association with ELISA positivity and use of an automatic milking system a negative association (OR = 0.3). Risk factors for PCR positivity were purchase of cattle from at least two delivery addresses (OR = 3.2), presence of cows with ticks (OR = 2.0), use of an automatic milking system (OR = 0.2) and presence of goats or sheep on the farm (OR = 0.4). Biosecurity and general hygiene seem associated with introduction and spread of C. burnetii in dairy herds.  相似文献   

17.
When a large-scale epidemic of porcine epidemic diarrhea (PED) occurred in 2013 in Japan, feedback feeding (feeding feces and gut tissues of infected piglets) was attempted to impart immunity to sows and immunize nursing piglets via breastfeeding. This study evaluated the effect of feedback feeding on PED control at 172 farms in Kagoshima and Miyazaki Prefectures. Univariable and multivariable generalized linear models were used to analyze the associations between conduct of feedback feeding and damage from the outbreak (outbreak period and the number of piglet deaths) at the farm level. The within-farm outbreak period shortened over time after the regional outbreak began on Kyushu Island (P=0.009) and was longer on large-scale farms (mean 66.0 days, P=0.003) than small-scale farms (29.4 days) and on farms that used feedback feeding (145.2 days, P=0.059) than those that did not (66.0 days). The number of dead piglets decreased over time since the first regional case (P<0.001) and was higher at farrow-to-finish farms (3.8 piglets/sow, P<0.001) than reproduction farms (0.7 piglets/sow). The effect of feedback feeding on the number of dead piglets was not significant, but its interaction term with farm style had a significant effect (5.0 more piglet deaths at reproduction farms than fallow-to-finish farms, P=0.001). These results suggest that feedback feeding made the damage from PED worse, though it was well established at a later stage of the regional PED epidemic.  相似文献   

18.
Herd and individual animal prevalence along with associated risk factors of bovine brucellosis was assessed on dairy farms located in 22 districts in Haryana and Punjab of India. Examination of 4,580 female animals of 119 dairy farms by Rose Bengal test and enzyme-linked immunosorbent assay revealed that an overall herd prevalence was 65.54 % (78/119) and individual animal prevalence was 26.50 % (1,214/4,580). Herd prevalence in Haryana was 62.79 % which was not significantly different (P?=?0.4208) from Punjab (72.72 %). Individual animal prevalence was 34.15 % in Punjab which was significantly higher (P?<?0.0001) than Haryana (22.34 %). Prevalence of brucellosis on dairy farms was detected in 20 of the 22 districts, of which 12 districts were in Haryana and 8 in Punjab. Risk factors such as species of animals, age of animals, herd size, awareness of dairymen for brucellosis, entry of a purchased animals on the farm, abortion on farm, use of calving pens, type of breeding, and type of farming were analyzed. The study indicated that the odds ratio (OR) was significant with risk factors of species (OR?=?1.63; 95 %CI?=?1.40–1.90; P?<?0.0001), age (OR?=?0.22; 95 %CI?=?0.17–0.29; P?<?0.0001), awareness of brucellosis among dairymen (OR?=?21.65; 95 %CI?=?2.63–178.04; P?=?0.0042), entry of purchased animal on the farm (OR?=?9.16; 95 %CI?=?2.38–35.18; P?=?0.0012), abortion in animals (OR?=?5.57; 95 %CI?=?1.92–16.10; P?=?0.0015) and on cow farm (OR?=?3.43; 95 %CI?=?1.33–8.82; P?=?0.0105). While the OR was insignificant (P?>?0.05) with risk factors of herd size, use of calving pen on farms, type of breeding and on buffalo and mixed type of farms.  相似文献   

19.
Infectious salmon anemia virus (ISAV) infection is a constant major threat to farmed and wild Atlantic salmon worldwide. Many epidemics have recently been reported in the most important salmon farming regions of the world, including Chile (2007–2009), where ISAV generated the most important disease and economic crisis in history of the salmon industry of the country. The spread of ISAV within a region is most likely by local or neighborhood spread from an infected farm; however, there is evidence that anthropogenic activities, such as movement of live or harvested fish or their byproduct, may have played a more important role than environmental or passive transmission in the 2007–2009 outbreak. Atlantic salmon farms (n = 421) were retrospectively followed from stocking to harvesting in southern Chile at the time of the ISAV epidemic (2007–2009). The effect of husbandry and spatial risk factors, in addition to contact-network risk factors, which were obtained from the social network analyses, on time to first ISAV infection was estimated using a multivariable Cox proportional hazards model. Five variables were retained in the final fitted model: co-existing multiple generations on a farm (hazard ratio [HR] = 2.585), mean smolt weight at stocking greater than 120 g (HR = 1.165), farm area (per km2) (HR = 1.005), and increased number of shipments entering a farm, i.e. the farm input degree (HR = 1.876) were associated with reduced time to infection; whereas time-to-infection was longer for farms located farther from an ongoing ISAV outbreak (HR = 0.943). It was demonstrated that movements of latently infected fish resulted in approximately 7 outbreaks, and potentially explain about 6% of the total number of cases during the epidemic. Results from this study provide new information about the mechanisms of spread of ISAV in one the largest documented ISAV epidemics in the world. Findings may be used to support the design and implementation of risk-based surveillance and control programs that may help to prevent, detect and control future ISAV outbreaks.  相似文献   

20.
Rabbit sera (n = 1600) from 40 commercial farms were submitted to a serological screening for Encephalitozoon cuniculi by an enzyme-linked immunosorbent assay (ELISA) and a carbon immunoassay (CIA test). Antibodies anti-Encephalitozoon cuniculi were found in 505/1600 (31.6%) sera analysed, and all the farms (100%) resulted positive. Rabbits older than 4 months showed a significantly higher seropositivity for E. cuniculi (chi-squared test: p < 0.0001) than rabbits under 4 months, E. cuniculi sero-prevalence showed an increasing trend in rabbits within the farm along with the increase in the “number of rabbits on the farm”; however, this trend was not significant (Spearman’s correlation: p = 0.073).The findings of the present study confirm that rabbit is the main reservoir of E. cuniculi; they are of epidemiological relevance and immediate public health importance because of the recognized infectivity in humans by the microsporidium.  相似文献   

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