Abattoir prevalence, organ distribution, public health and economic importance of major metacestodes in sheep, goats and cattle in Fars, southern Iran

Some of the metacestodes are not only zoonotic but are also responsible for severe tissue damage, reduction in milk and meat production, and considerable economic loss due to condemnation of the infected organs of the herbivorous animals. The aim of the present study was to determine the prevalence of Cysticercus ovis, Cysticercus tenuicollis, hydatid cyst and Coenurus gaigeri in sheep and goats and Cysticercus bovis, Cysticereus tenuicollis and hydatid cyst in cattle. A total of 1050 sheep, 950 goats and 500 cattle slaughtered at Shiraz Slaughterhouse were carefully examined for these metacestodes. Cysticercus tenuicollis was found in 184 (17.52%) sheep and 523 (55.05%) goats. The prevalence of C. tenuicollis was higher in males than females (P<0.01), and was higher in goats compared to sheep (P<0.01). Hydatid cyst was found in 478 (45.52%) sheep and 95 (10.0%) goats and its prevalence was higher in older animals compared to the younger ones. Coenurus gaigeri was found in 5 (0.48%) sheep and 17 (1.79%) goats and Cysticercus ovis was found in one male sheep only (0.09%). Cysticercus bovis was found in 3 male cattle (0.6%) and hydatid cyst was found in 58 (11.6%) cattle. The prevalence of hydatid cyst was higher in older cattle compared to the younger ones and higher in females than males. These results suggest that the high prevalence of the metacestodes infestations in this area is a great concern for both medical and veterinary authorities to design therapeutic and preventive programs to overcome this problem.

Diagnosis of cattle diseases endemic to sub-Saharan Africa: evaluating a low cost decision support tool in use by veterinary personnel

BACKGROUND

Diagnosis is key to control and prevention of livestock diseases. In areas of sub-Saharan Africa where private practitioners rarely replace Government veterinary services reduced in effectiveness by structural adjustment programmes, those who remain lack resources for diagnosis and might benefit from decision support.

METHODOLOGY/PRINCIPAL FINDINGS

We evaluated whether a low-cost diagnostic decision support tool would lead to changes in clinical diagnostic practice by fifteen veterinary and animal health officers undertaking primary animal healthcare in Uganda. The eight diseases covered by the tool included 98% of all bovine diagnoses made before or after its introduction. It may therefore inform proportional morbidity in the area; breed, age and geographic location effects were consistent with current epidemiological understanding. Trypanosomosis, theileriosis, anaplasmosis, and parasitic gastroenteritis were the most common conditions among 713 bovine clinical cases diagnosed prior to introduction of the tool. Thereafter, in 747 bovine clinical cases estimated proportional morbidity of fasciolosis doubled, while theileriosis and parasitic gastroenteritis were diagnosed less commonly and the average number of clinical signs increased from 3.5 to 4.9 per case, with 28% of cases reporting six or more signs compared to 3% beforehand. Anaemia/pallor, weakness and staring coat contributed most to this increase, approximately doubling in number and were recorded in over half of all cases. Finally, although lack of a gold standard hindered objective assessment of whether the tool improved the reliability of diagnosis, informative concordance and misclassification matrices yielded useful insights into its role in the diagnostic process.

CONCLUSIONS/SIGNIFICANCE

The diagnostic decision support tool covered the majority of diagnoses made before or after its introduction, leading to a significant increase in the number of clinical signs recorded, suggesting this as a key beneficial consequence of its use. It may also inform approximate proportional morbidity and represent a useful epidemiological tool in poorly resourced areas.

Prevalence and prevention of paratuberculosis in North America

The United States of America (U.S.) has made several attempts over the years to develop a producer accepted voluntary program. The focus of the U.S. Voluntary Bovine Johne's Disease Control Program (VBJDCP) is to provide producers with the tools to control Johne's disease on their farms and identify herds with a low risk for the presence of Mycobacterium avium subspecies paratuberculosis (MAP) infection. The VBJDCP includes an evaluation of producers' operations to identify practices that could allow the transmission of MAP among animals or between premises. Once risky practices havebeen identified, a herd management plan is developed to assist the producer in correcting risky practices. In addition to management changes, vaccination is a control tool allowed in the U.S. because it reduces the clinical signs of Johne's disease and the shedding of MAP. Testing is used in addition to management changes. While the classification component of the VBJDCP dictates the amount and type of testing herd owners are required to conduct, the education and management components of the VBJDCP does not specify testing protocols. The testing for control is intended to fit the needs and resources of producers and can be quite flexible. Management changes on the farm remain the key to control and programs cannot replace well thought out plans by producers that are specific to their resources, facilities, and operation.

Examples and suggestions for the control of paratuberculosis in European cattle

Paratuberculosis, or Johne's disease (JD), is caused by Mycobacterium avium subspecies paratuberculosis (MAP), is found in ruminants worldwide and can cause considerable economic losses in cattle. Control efforts and programs for JD in cattle are very diverse among European states, in Austria clinical JD is rated as a notifiable disease since 2006. The voluntary control programs established in many European countries, show different aims, measurements and acceptance. Most control programs for JD are based on a test and cull strategy, combined with hygienic precautions. Unfortunately, the willingness to participate in such programs by farmers and veterinarians is limited due to high costs, intensive workload, long duration and limited success. To overcome this drawback and to harmonize the control of MAP in Europe, a basic program with defined minimum standards is suggested. This "minimal program" for the control of JD in cattle consists of 3 steps. Step 1 includes diagnostic evaluation of every case of diarrhea in adult cattle and culling of animals with clinical JD. Step 2 is the implementation of basic management measures, adapted to the potentials of the individual farm. Step 3 consists of regularly evaluation of the MAP-herd status with the focus on MAP-shedding animals. This basic control program can be performed with reasonable costs and work load in most cattle herds and might serve as an international minimum standard for MAP-control in cattle. Such a program can also pose an incentive to decrease MAP-infections for those not willing to participate in more sophisticated control programs.

Economic impact of stable flies (Diptera: Muscidae) on dairy and beef cattle production

Stable flies, Stomoxys calcitrans (L.), are among the most damaging arthropod pests of cattle worldwide. The last estimate of their economic impact on United States cattle production was published 20 yr ago and placed losses at $608 million. Subsequently, several studies of effects of stable flies on beef cattle weight gain and feed efficiency have been published, and stable flies have become increasingly recognized as pests of cattle on pasture and range. We analyzed published studies and developed yield-loss functions to relate stable fly infestation levels to cattle productivity, and then estimated the economic impact of stable flies on cattle production in the United States. Four industry sectors were considered: dairy, cow-calf, pastured stockers, and feeder cattle. In studies reporting stable fly infestation levels of individual herds, median annual per animal production losses were estimated to be 139 kg of milk for dairy cows, and 6, 26, and 9 kg body weight for preweanling calves, pastured stockers, and feeder cattle, respectively. The 200,000 stable flies emerging from an average sized winter hay feeding site reduce annual milk production of 50 dairy cows by an estimated 890 kg and weight gain of 50 preweanling calves, stockers, or feeder cattle by 58, 680, or 84 kg. In 2009 dollars, the value of these losses would be $254, $132, $1,279, or $154, respectively. Using cattle inventories and average prices for 2005-2009, and median monthly infestation levels, national losses are estimated to be $360 million for dairy cattle, $358 million for cow-calf herds, $1,268 million for pastured cattle, and $226 million for cattle on feed, for a total impact to U.S. cattle industries of $2,211 million per year. Excluded from these estimates are effects of stable flies on feed conversion efficiency, animal breeding success, and effects of infested cattle on pasture and water quality. Additional research on the effects of stable flies on high-production dairy cows and nursing beef calves is needed to increase the reliability of the estimates.

Seroprevalence of Anaplasma marginale in 2 Iowa feedlots and its association with morbidity, mortality, production parameters, and carcass traits

A prospective cohort observational study was conducted to investigate the seroprevalence of Anaplasma marginale in Iowa feedlots and its association with morbidity, mortality, and treatment costs. Blood samples were taken from 659 calves from 31 consigners at processing and classified as seropositive to A. marginale using a competitive enzyme-linked immunosorbent assay (cELISA) with a 30% cutoff. Health and production parameters were modeled by A. marginale serostatus with mixed model regression analysis. The apparent prevalence of seropositive cattle was 15.17% (100/659). When the cELISA positive cutoff was at 42% inhibition, the apparent prevalence was 5.00% (33/659). There was no significant association between A. marginale serostatus and production parameters; however, seropositive status had a weak positive association with undifferentiated fever (P = 0.17). Although prevalence of anaplasmosis in Iowa feedlots is higher than reported in Montana-sourced calves arriving in Canadian feedlots, this was not associated with increased production costs.

Bovine fasciolosis: prevalence, effects of treatment on productivity and cost benefit analysis in five districts of Punjab, Pakistan

The present study reports the prevalence, effects of treatment and cost benefit analysis of bovine fasciolosis in five districts of Punjab Province viz Sargodha, Jhang, Muzaffargarh, Lodhran and Layyah. From each of the five districts, 80 animals were selected and fortnightly screened through standard coprological procedures for a period of one year for the presence of eggs of Fasciola species. Of 4800 faecal samples analyzed, 1222 (25.46%) were found positive for fasciolosis. The occurrence of Fasciola (F.) gigantica (22.40%) was higher (P<0.05) than F. hepatica (3.06%). Highest month-wise prevalence (P<0.05) of fasciolosis was found in winter (39.08%) followed in decreasing order by spring (29.50%), autumn (20.33%) and summer (12.92%). District-wise prevalence of fasciolosis was highest (P<0.05) in Sargodha (40.31%) and lowest in Layyah (11.77%) while other districts were having intermediate values of prevalence of fasciolosis. Species-wise prevalence of fasciolosis was found higher (P<0.05) in buffaloes (30.50%) as compared to cattle (20.42%). However, there were no age and sex-related differences (P>0.05) in prevalence of fasciolosis. A strong positive association of grazing (OR=1.81), mixed farming of small and large ruminants (OR=1.39), stagnant pond bathing (OR=2.24) and river/canal bathing (OR=2.06) was found with the prevalence of fasciolosis as compared to stall feeding, separate farming of small and large ruminants and rivers/canal/tap water bathing, respectively. Post-treatment average milk increase of 0.62 L per animal per day with 0.35% higher fat was observed in fasciolicide-treated animals with the cost benefit ratio of 3.9. The results provided significant data on the epidemiology of five districts of Punjab province which may be helpful for the planners and small holder dairy farmers for control of fasciolosis in the study districts.

Current status of ruminant theileriosis and its economical impact in Turkey

The diagnosis of ruminant theileriosis in Turkey is based on microscopical examination of thin blood and lymph smears, serology, traditional staining methods of the salivary glands of ticks and molecular techniques. Although some investigators reported that T. mutans was found in cattle with microscopic examination (7.4%-36.7%) and experimental study, they did not detect this parasite using molecular techniques. On the other hand, the prevalence of T. buffeli/orientalis was found to differ between 0.9% and 13.6% using molecular techniques in different regions of Turkey. Tropical theileriosis caused by T. annulata is widespread, and constitutes a major health and management problem in cattle in Turkey. The economic losses resulting from the tropical theileriosis were estimated to be US $598,000, $133,000 and $130,000 in the endemic stable zones of Turkey. Microscopic prevalence of T. annulata has been reported to be between 0% and 60.5% in different parts of Turkey. The serologic prevalence of T. annulata was found to differ between 1.8% and 91.4% by IFAT. In subsequent studies, the prevalence of this parasite was found to differ between 15.4% and 61.2% by molecular techniques. Clinical cases of ovine theileriosis have not been documented in Turkey. The prevalence of T. ovis/recondita was found to differ between 0% and 41.3% by microscopic examination of thin blood smears and its seroprevalence was found to be between 8.2% and 63.2% by IFAT. This parasite has also been reported to be present between 41.8% and 67.7% by molecular techniques.

Evaluation of the Voluntary Johne's Disease Herd Status Program as a source of replacement cattle

The objectives of this study were to evaluate the perceived value that enrolled producers gained from participation in the Voluntary Johne's Disease Herd Status Program (VJDHSP), and to evaluate the risk of infection with Mycobacterium avium ssp. paratuberculosis (MAP) of cattle reared in a presumed Johne's free environment vs. cattle raised in an environment of unknown Johne's status. Producers enrolled in level 3 or 4 of the VJDHSP (98 and 99% probability, respectively, of being free from MAP infection) were interviewed via telephone. Producers were asked questions pertaining to their participation in the VJDHSP, and asked to identify herds to which they had sold replacement heifers. These cattle were presumed to be uninfected before sale. Fifty-nine cattle (identified as having been purchased into infected herds as heifers) were identified as having been raised in uninfected herds and sold to producers with herds of unknown Johne's disease status. On the purchasing farm, fecal and blood samples were collected from each cow of VJDHSP origin and 3 randomly selected home-reared cows per VJDHSP cow matched by lactation as controls. Samples were tested using commercial ELISA (serum) and bacterial culture (feces). Results indicated that enrolled producers saw value in VJDHSP participation, and that cattle reared in VJDHSP herds were less likely to be infected with MAP than herdmates as measured by serum ELISA MAP antibody and by fecal culture. This study provides evidence of the value of the VJDHSP in providing economic value to participants and supports the promotion of VJDHSP herds as a source of replacement cattle of low infection risk for MAP.

Use of treatment records and lung lesion scoring to estimate the effect of respiratory disease on growth during early and late finishing periods in South African feedlot cattle

Growth, morbidity, and slaughter data from 2,036 calves in 2 South African feedlots were used to estimate the effect of bovine respiratory disease (BRD) and of lung lesion type and extent on growth during the early (processing to d 35) and late (d 35 to slaughter) finishing periods. Calves were weighed at processing (d 5 after arrival), on d 35, and at slaughter after a mean of 137 d on feed. All calves were monitored twice daily and were treated for BRD if rectal temperature was > 40 degrees C or if other specific signs of BRD were present. After slaughter, the occurrence and extent of parenchymal bronchopneumonic lesions and pleural adhesions were recorded. Subclinical BRD (never treated but with lung lesions at slaughter) occurred in 29.7% and clinical BRD in 22.6% of calves. Lung lesions were present in 43% of calves at slaughter; 8.6% had parenchymal lesions and 38.8% had pleural adhesions. Using a combined case definition (treated for BRD and/or lung lesions present at slaughter), the incidence of BRD was 52.5%. During the early finishing period, clinical BRD reduced ADG by 216 g (P < 0.001), subclinical BRD reduced ADG by 91 g (P < 0.001), and the combined effect of BRD was a 143 g reduction in ADG (P < 0.001). After d 35, animals treated for BRD tended to grow faster than those with subclinical BRD (P = 0.11), indicating that treatment was generally successful in reducing economic losses. The extent of bronchopneumonic lesions at slaughter was not associated with reduced growth during the early finishing period (P = 0.27), but extensive lesions reduced ADG by 88 g during the late period (P = 0.02). In contrast, the extent of pleural adhesions was not associated with reduced growth rate during the late finishing period (P = 0.37) but was strongly associated with reduced ADG before d 35; there was a 101 g reduction (P < 0.001) and a 220 g reduction (P = 0.01) for adhesions involving < 50% and > 50% of the pleural surfaces, respectively. Thus, although the presence of bronchopneumonic lesions and pleural adhesions at slaughter were both associated with reductions in overall ADG, they were indicative of production losses having occurred at different times during the finishing period. The overall effect of BRD was a 24 g reduction in ADG (P = 0.02) and a 5.1 d increase in days on feed (P < 0.001). The hidden cost of reduced growth rate due to BRD amounted to $3.41 per calf with clinical or subclinical BRD, or $1.79 per animal entering the feedlot.

Prevalence of cystic echinococcosis in slaughtered cattle in Afyonkarahisar

This study was carried out in 1001 cattle that were slaughtered in 3 abattoirs in the Afyonkarahisar district of western Turkey. Abattoirs were visited twice a week and internal organs of the cattle were examined for cystic echinococcosis (CE). The number of organs discarded because of CE was recorded. CE was found in 295 (29.47%) out of 1001 cattle studied. CE was found in 113 (44.31%) out of 255 cows and 182 (24.39%) out of 746 bulls. This difference was statistically significant (p < 0.001). CE was observed only in liver of 130 (44.06%) cattle, only in lungs of 91 (30.85%); only in hearts of 2 (0.68%) and only in the kidney of 1 (0.34%); in both livers and lungs of 70 (23.73%), and in both hearts and lungs of 1 (0.34%). Also, the rate of CE was significantly higher in cows than bulls in terms of organ predilection (p < 0.001). Forty three livers were completely discarded along with half of 18 livers, a quarter of 37 livers and the remaining livers in various degrees. Forty four lungs were completely destroyed along with half of 13 and a quarter of 21 whereas 3 hearts and one kidney were completely destroyed. The fertility rate of cysts was found to be 5.42%. In this study the prevalence of CE in cattle in Afyonkarahisar district has been documented and possible economic losses due to CE were emphasized.

Simulation model for evaluation of testing strategies for detection of paratuberculosis in Midwestern US dairy herds

We developed a stochastic simulation model to compare the herd sensitivity (HSe) of five testing strategies for detection of Mycobacterium avium subsp. paratuberculosis (Map) in Midwestern US dairies. Testing strategies were ELISA serologic testing by two commercial assays (EA and EB), ELISA testing with follow-up of positive samples with individual fecal culture (EAIFC and EBIFC), individual fecal culture (IFC), pooled fecal culture (PFC), and culture of fecal slurry samples from the environment (ENV). We assumed that these dairies had no prior paratuberculosis-related testing and culling. We used cost-effectiveness (CE) analysis to compare the cost to HSe of testing strategies for different within-herd prevalences. HSe was strongly associated with within-herd prevalence, number of Map organisms shed in feces by infected cows, and number of samples tested. Among evaluated testing methods with 100% herd specificity (HSp), ENV was the most cost-effective method for herds with a low (5%), moderate (16%) or high (35%) Map prevalence. The PFC, IFC, EAIFC and EBIFC were increasingly more costly detection methods. Culture of six environmental samples per herd yielded >or=99% HSe in herds with >or=16% within-herd prevalence, but was not sufficient to achieve 95% HSe in low-prevalence herds (5%). Testing all cows using EAIFC or EBIFC, as is commonly done in paratuberculosis-screening programs, was less likely to achieve a HSe of 95% in low than in high prevalence herds. ELISA alone was a sensitive and low-cost testing method; however, without confirmatory fecal culture, testing 30 cows in non-infected herds yielded HSp of 21% and 91% for EA and EB, respectively.

Pregnancy loss in dairy cows: the contributing factors, the effects on reproductive performance and the economic impact

This study investigated the effects of the herd, cow parity, the insemination protocol and season on the incidence of pregnancy loss (PL) in dairy herds. Furthermore, we determined the downstream effects of PL on reproductive performance and its economic impact. The overall incidence rate of PL was 6.9% in 1,001 pregnant cows and its incidence peaked (p < 0.01) during the second trimester of gestation. GLIMMIX analysis revealed that cow parity was the important risk factor for the PL. The odds ratio showed that the likelihood of PL in cows with parities of 1 or 2 was decreased by 0.6 or 0.5 fold compared to the cows with a parity of 3 or higher. Following PL, the mean rate of endometritis was 23.2% and endometritis was more common (p < 0.05) when PL occurred during the third trimester than during the first and second trimesters. The mean culling rate was 46.4% and this did not differ with the period of PL. The overall mean intervals from PL to the first service and conception were 63.4 and 101.8 days, respectively. The mean interval from PL to first service was longer (p < 0.01) for cows with PL during the third trimester than for the cows with PL during the first and second trimesters. The economic loss resulting from each PL was estimated at approximately $2,333, and this was largely due to an extended calving interval and increased culling. These results suggest that cow parity affects the incidence of PL, which extends calving interval and causes severe economic loss of dairy herds.

Impact of Calving Ease on Functional Longevity and Herd Amortization Costs in Basque Holsteins Using Survival Analysis

The aim of this study was to analyze the impact of calving ease (CE) on functional longevity of Basque Holsteins, using a Weibull proportional hazards model. The data considered for the analysis were 53,353 calving records from 25,810 Holstein cows distributed across 781 herds and sired by 746 bulls. The effects included in the statistical model were age at first calving, stage of lactation, interaction between year and season of calving, 305-d adjusted milk yield, CE, herd, and sire. Calving ease was considered as a time-dependent covariate and, as was the case for the rest of covariates included in the model, had a significant effect on functional longevity. Calvings needing assistance or surgery increased culling risk by 18%, when compared with unassisted calvings. The effect of CE on length of productive life in primiparous and multiparous cows was also investigated. A second analysis was performed replacing the CE effect with the interaction between parity and CE to evaluate the effect of CE in primiparous and multiparous cows. An increase in calving difficulty had a greater impact on culling during first lactations than in subsequent ones. Therefore, difficult calvings, mainly at first parities, had a high impact on herd amortization costs, increasing them by 10% in relation to easy calvings. Therefore, calving difficulty should be avoided as much as possible, especially in primiparous cows, to avoid reduction of profitability.

A stochastic simulation model to determine the sample size of repeated national surveys to document freedom from bovine herpesvirus 1 (BoHV-1) infection

Background

International trade regulations require that countries document their livestock's sanitary status in general and freedom from specific infective agents in detail provided that import restrictions should be applied. The latter is generally achieved by large national serological surveys and risk assessments. The paper describes the basic structure and application of a generic stochastic model for risk-based sample size calculation of consecutive national surveys to document freedom from contagious disease agents in livestock.

Methods

In the model, disease spread during the time period between two consecutive surveys was considered, either from undetected infections within the domestic population or from imported infected animals. The @Risk model consists of the domestic spread in-between two national surveys; the infection of domestic herds from animals imported from countries with a sanitary status comparable to Switzerland or lower sanitary status and the summary sheet which summed up the numbers of resulting infected herds of all infection pathways to derive the pre-survey prevalence in the domestic population. Thereof the pre-survey probability of freedom from infection and required survey sample sizes were calculated. A scenario for detection of infected herds by general surveillance was included optionally.

Results

The model highlights the importance of residual domestic infection spread and characteristics of different import pathways. The sensitivity analysis revealed that number of infected, but undetected domestic herds and the multiplicative between-survey-spread factor were most correlated with the pre-survey probability of freedom from infection and the resulting sample size, respectively. Compared to the deterministic pre-cursor model, the stochastic model was therefore more sensitive to the previous survey's results. Undetected spread of infection in the domestic population between two surveys gained more importance than infection through animals of either import pathway.

Conclusion

The model estimated the pre-survey probability of freedom from infection accurately as was shown in the case of infectious bovine rhinotracheitis (IBR). With this model, a generic tool becomes available which can be adapted to changing conditions related to either importing or exporting countries.

The prevalence and economic significance of Fasciola gigantica and Stilesia hepatica in slaughtered animals in the semi-arid coastal Kenya

Fasciola gigantica and Stilesia hepatica constrain ruminant productivity. The prevalence and economic losses caused by F. gigantica and S. hepatica in the ruminant production systems of Taveta division of Kenya were estimated in a retrospective appraisal of the slaughter records on the total number of animals slaughtered and livers condemned over the period 1989 to 2004. Only liver condemnations based on infestation by F. gigantica and S. hepatica were considered for purposes of this study. Liver condemnation rates differed significantly between bovines, caprines and ovines (p < or = 0.05) for F. gigantica (26%, 6.6% and 5.2%, respectively) and for S. hepatica (0.4%, 22% and 28%, respectively). The total loss through condemnation of both F. gigantica and S. hepatica infested livers was 4,408,272 KES (Kenyan shillings) (US dollars 72,272). The proportion of loss in bovines, caprines and ovines, was 76%, 17% and 7%, respectively. Fasciolosis contributed 3505410 KES (79.5%) and S. hepatica infestation 903,210 KES (20.5%) to the total losses due to liver condemnations. The authors feel strongly that there is a need for more work on the two parasites using live animals to determine the prevalence in animals of various ages, species and breeds and the economics of disease control at farm level.

Simulated economic effects of improving the sensitivity of a diagnostic test in paratuberculosis control

Low sensitivity (Se) of diagnostic tools is often mentioned as a major problem in the control of paratuberculosis (PTB) and much effort is put into the improvement of these tests. The hypothetical perspectives of improving the Se of a milk-antibody ELISA (hereafter: milk-ELISA) used in test-&-cull strategies against PTB in dairy cattle were investigated by simulations. The current Se varies between 10 and 80%, increasing with increasing lactation stage, parity and infection stage. We simulated the effects on a dairy herd's production of improving this Se to 80% (independent of these factors) and assumed no concomitant decrease in specificity. By using a PTB model called PTB-Simherd, 12 scenarios were simulated to study three test-&-cull strategies in each of four herds with 200 dairy cows. To show the maximal effect of using test-&-cull with such an improved test we simulated three strategies: (1) no testing, (2) testing with milk-ELISA test with the current Se and culling of positive cows immediately and (3) testing with milk-ELISA test with a Se improved to 80% and culling positive cows immediately. The four herds were defined by a moderate (25%) or high (80%) initial true within-herd prevalence (including young stock), and a poor or good heat-detection success of 40 or 60%. We assumed that these factors influenced the effects of improving the Se of the milk-ELISA. Management both concerning calf management and in general was specified to represent a typical Danish herd. Using an improved milk-ELISA was predicted to reduce the prevalence of PTB more effectively than the current ELISA, and over 10 years bring the production of a herd with moderate initial prevalence up to a production level comparable to a non-infected herd (unlike if the current ELISA had been used). In a herd with high initial prevalence (80%) milk production was increased more by using the improved milk-ELISA, but after 10 years the replacement rate was still very high causing problems with having enough recruitment animals-especially in high-prevalence herds with poor reproductive performance. Economically important measurements in all four herds benefited from the improvement of the test over a 10-year period. However, in the first 3-5 years the improved test would be more expensive to use than the current test, due to increased replacement (reduced net annual revenue per cow euro15 on average) but after that, net annual revenue increased continuously; after 10 years it was euro70-90 higher, than if the current milk-ELISA was used. Also, the milk-ELISA test with its current Se seemed to be profitable already after 2 years in high-prevalence herds using a test-&-cull strategy based on the milk-ELISA alone.

Associations between anti-Fasciola hepatica antibody levels in bulk-tank milk samples and production parameters in dairy herds

Our primary objective was to determine the relationships between Fasciola-specific antibody levels in bulk-tank milk and measures of productivity to estimate economic losses that are associated with Fasciola infections. A bulk-tank milk sample was collected in March 2004 from 1105 dairy herds in Flanders and the antibody levels against Fasciola hepatica (ODRf) and Ostertagia ostertagi (ODRo) were determined. The association of ODRf with four production parameters (milk yield, milk-protein %, milk-fat % and inter-calving interval) was assessed by multivariable linear-regression models. Production data were available for 463 out of the 1105 herds sampled. An increase in ODRf from the 25% quantile (0.428) to the 75% quantile (1.064) was associated with a decrease in the annual average milk yield of 0.7kg/(cowday) (P=0.002), with a decrease in the average milk-fat % of 0.06% (P<0.001) and with an increase of the mean inter-calving interval of 4.7 days (P=0.03). No significant relationship was found with the average milk-protein %. When the relationships of ODRf and ODRo with milk yield were tested simultaneously, we saw an additive rather than synergistic effect of concurrent infections.