Failure costs associated with mastitis in smallholder dairy farms keeping Holstein Friesian × Zebu crossbreed cows.

Mastitis is a costly disease and in many areas of the world, these costs have been quantified to support farmers in their decision making with regard to prevention of mastitis. Although for subsaharan circumstances estimates have been made for the costs of subclinical mastitis (SCM), farm-specific cost estimations comprising both clinical mastitis (CM) and SCM are lacking. In this paper, we quantified failure costs of both CM and SCM on 150 Ethiopian market-oriented dairy farms keeping Holstein Friesian × Zebu breed cows. Data about CM were collected by face-to-face interviews and the prevalence of SCM was estimated for each farm using the California mastitis test. All other relevant information needed to calculate the failure costs, such as the consequences of mastitis and price levels, was collected during the farm visits, except for the parameter for milk production losses due to SCM, which was based on literature estimates and subjected to sensitivity analyses. The average total failure costs of mastitis was estimated to be 4 765 Ethiopian Birr (ETB) (1 ETB = 0.0449 USD) per farm per year of which SCM contributed 54% of the costs. The average total failure costs per lactating cow per farm per year were 1 961 ETB, with a large variation between farms (range 0 to 35 084 ETB). This large variation in failure costs between farms was mainly driven by variation in incidence of CM and prevalence of SCM. Milk production losses made the largest contribution (80%), whereas culling contributed 13% to 17% to the total failure costs. In our estimates, costs of veterinary services, drugs, discarded milk and labour made a minor contribution to the total failure costs of mastitis. Relative to the income of dairy farmers in North Western Ethiopia; the total failure costs of mastitis are high. In general, Ethiopian farmers are aware of the negative consequences of CM, but creating awareness of the high costs of SCM and showing large variation between farmers may be instrumental in motivating farmers to also take preventive measures for SCM.

Characterization of Staphylococcus aureus isolated from milk samples of dairy cows in small holder farms of North-Western Ethiopia.

BACKGROUND: Staphylococcus aureus is a contagious, opportunistic pathogen that causes clinical or subclinical mastitis in dairy cattle. The genetic background and antimicrobial resistance of isolates from Ethiopian dairy farms has not been studied. Therefore, the aim of this study was to characterize S. aureus from Ethiopian hand milked dairy cows, by spa, MLST and virulence factor typing, and by assessment of antimicrobial susceptibility. A total of 79 S. aureus isolates from intramammary infections was studied. A PCR was used to detect lukM-lukF' and pvl genes encoding the bovine and human associated bi-component leukocidins, and the toxic shock syndrome toxin gene-1 (tst). Antimicrobial susceptibility was determined using the broth microdilution method. RESULTS: Twenty different spa types were identified, most isolates were t042 (58%), and the closely related t15786 (11%). The proportion of isolates positive for lukM-lukF', tst and pvl was low at 0.04, 0.10 and 0.09 respectively, with lukM-lukF' often co-occurring with tst, but not with pvl. Methicillin-resistance was not found, but resistance to penicillin/ampicillin (86%) and tetracycline (54%) was very common. CONCLUSIONS: We found a high degree of relatedness among bovine S. aureus isolates in North-Western Ethiopia, suggesting contagious within and between farm transmission of strains that are often resistant to commonly used antimicrobials. This highlights the need for effective preventive measures that aim at limiting transmission of bacteria rather than using antimicrobials to control S. aureus mastitis in Ethiopia.

Prevalence of subclinical mastitis and associated risk factors at cow and herd level in dairy farms in North-West Ethiopia.

Knowledge of mastitis pathogens and their predominance as well as understanding of risk factors are prerequisites to improve udder health in a herd, region or country. In Ethiopia, such information is scarce, despite the fact that mastitis is an important cattle disease in the country. A cross-sectional study that describes prevalence and causative agents of subclinical mastitis (SCM) as well as risk factors at cow and herd level was conducted on 167 dairy farms in North-West Ethiopia. On average, 33% of the quarters and 62% of the cows were California Mastitis Test (CMT) positive, but the within herd quarter level prevalence ranged between 0 and 100%. A total of 1543 milk samples, being 27 quarters that showed signs of CM, 606 CMT positive quarters and 910 CMT negative quarters were cultured, respectively 40%, 67% and 47% was positive on bacteriological culture. Coagulase negative staphylococci (CNS) (31%) followed by Staphylococcus aureus (9%) were the pathogens most frequently isolated. Based on face-to-face questionnaire data, 35 herd level and 13 cow level factors were evaluated for their association with SCM (based on CMT) and with a positive culture for any bacteria, CNS or S. aureus. Cows with a history of CM, of higher parity, >150days in milk (DIM) and herds with owners that have >10th grade level of education had higher odds of SCM. The odds of being culture positive for any bacteria was higher in cows with ≥25% Holstein Friesian blood level (HBL), >150 DIM, housed on cemented floors, and milked by squeezing rather than stripping. Similarly, the odds of culturing CNS was higher in cows with 25-50% HBL, >150 DIM, and milked by squeezing. Staphylococcus aureus was more often found in cows with a history of CM and in larger herds. Checking the udder for mastitis, feeding cows according to their requirements and allowing calves to suckle the cows were negatively associated with SCM, with culturing any bacteria and with culturing CNS, respectively. Higher odds of SCM and of culturing CNS were found in herds owned by members of a dairy cooperative. In summary, we identified a high prevalence of SCM and intramammary infections with substantial variation between farms, and we found a number of risk factors explaining this variation. The risk factors for mastitis that were identified in this study can form the basis of an udder health control program specific for the dairy industry in North-West Ethiopia.

Challenging the Wigglesworthia, Sodalis, Wolbachia symbiosis dogma in tsetse flies: Spiroplasma is present in both laboratory and natural populations.

Profiling of wild and laboratory tsetse populations using 16S rRNA gene amplicon sequencing allowed us to examine whether the "Wigglesworthia-Sodalis-Wolbachia dogma" operates across species and populations. The most abundant taxa, in wild and laboratory populations, were Wigglesworthia (the primary endosymbiont), Sodalis and Wolbachia as previously characterized. The species richness of the microbiota was greater in wild than laboratory populations. Spiroplasma was identified as a new symbiont exclusively in Glossina fuscipes fuscipes and G. tachinoides, members of the palpalis sub-group, and the infection prevalence in several laboratory and natural populations was surveyed. Multi locus sequencing typing (MLST) analysis identified two strains of tsetse-associated Spiroplasma, present in G. f. fuscipes and G. tachinoides. Spiroplasma density in G. f. fuscipes larva guts was significantly higher than in guts from teneral and 15-day old male and female adults. In gonads of teneral and 15-day old insects, Spiroplasma density was higher in testes than ovaries, and was significantly higher density in live versus prematurely deceased females indicating a potentially mutualistic association. Higher Spiroplasma density in testes than in ovaries was also detected by fluorescent in situ hybridization in G. f. fuscipes.

Comparison of 3 tests to detect acaricide resistance in Boophilus decoloratus on dairy farms in the Eastern Cape Province, South Africa.

The susceptibility of the larval offspring of engorged female Boophilus decoloratus, and of the engorged females, collected from cattle on the dairy farms Brycedale, Sunny Grove and Welgevind in the Eastern Cape Province, South Africa, was tested against the acaricides amitraz, chlorfenvinphos and cypermethrin. Resistance was determined by means of the Shaw Larval Immersion Test (SLIT) for larvae and the Reproductive Estimate Test (RET) and Egg Laying Test (ELT) for adults. At Brycedale the tests all indicated resistance to chlorfenvinphos, and RET and ELT indicated resistance to amitraz and emerging resistance to cypermethrin. At Sunny Grove, B. decoloratus was resistant to cypermethrin using SLIT and exhibited emerging resistance to chlorfenvinphos with SLIT and to cypermethrin with both RET and ELT At Welgevind, resistance was recorded against chlorfenvinphos (SLIT) and against cypermethrin (ELT), and emerging resistance against permethrin (RET). The results obtained with RET and ELT were generally comparable, but often differed from those obtained with SLIT. Resistance could be detected within 7 days with ELT compared to 42 days with RET and 60 days with SLIT.

Acaricide resistance profiles of single- and multi-host ticks from communal and commercial farming areas in the Eastern Cape and North-West Provinces of South Africa.

A field study (February 2000 to August 2001) was conducted on communal and commercial farms in the Eastern Cape and North-West Provinces of South Africa to detect the levels of tick resistance to commonly used acaricides. The larvae obtained from engorged females of the one-host tick Boophilus decoloratus, the two-host tick Rhipicepalus evertsi evertsi and the three-host ticks Amblyomma hebraeum and Rhipicephalus appendiculatus were tested against various concentrations of amitraz, chlorfenvinphos and cypermethrin using the Shaw Larval Immersion Test method. Ticks from the communal farms showed higher levels of resistance to cypermethrin and some resistance to chlorfenvinphos whilst no resistance was detected against amitraz. However, ticks from commercial farms were equally resistant to amitraz, chlorfenvinphos and cypermethrin. The B. decoloratus populations tested were considerably more resistant to all the acaricides tested than the R. evertsi evertsi, A. hebraeum and R. appendiculatus populations. This supports the hypothesis that single-host ticks develop resistance faster than multi-host ticks. This trend was recorded on most of the farms where single- and multi-host ticks co-existed. It was concluded that the use of acaricides at high frequencies and high concentrations was one of the main causes of tick resistance in the study areas. Possible factors which caused the resistance problems are discussed and acaricide management strategies recommended.

In vivo evaluation of amitraz against ticks under field conditions in Ethiopia.

An aqueous emulsion of amitraz (Bovitraz, Bayer AH), prepared and applied according to the manufacturer's recommendations, was evaluated for its activity against cattle ticks on a dairy farm in Ethiopia. Eight crossbred heifer calves aged between 6 and 8 months and heavily infested with ticks were selected and divided into equal treatment and control groups. The calves in the treatment group were hand-sprayed with the amitraz emulsion while the control group was left untreated. Each calf was restrained and ticks were counted and identified in situ. One hundred percent tick control was achieved on Day 3 after acaricide application, and this was maintained for a further 18 days. The residual effect was long, and protected the animals from re-infestation for 21 days. There was a significant difference between the mean number of ticks on the control group compared to the treated group (P < 0.05). An important finding in this trial was the rapid detachment of all tick instars from animals treated with the test acaricide.

The distribution of ixodid ticks (Acari: Ixodidae) in central Ethiopia.

Ixodid ticks were collected from domestic animals, mainly cattle, in 11 administrative zones covering 84 districts in central Ethiopia over a period of 2 years (July 1996 to June 1998). Nineteen tick species were identified. Four of these belonged to the genus Amblyomma, one to Boophilus, two to Haemaphysalis, three to Hyalomma and nine to Rhipicephalus. Amblyomma variegatum and Rhipicephalus evertsi evertsi were present in all 11 administrative zones and, with the exception of Afar, Boophilus decoloratus was present in nearly every district in which collections were made. These three species constituted more than 50% of all ticks collected. Amblyomma cohaerens and Rhipicephalus bergeoni were common in the west of the survey region and Rhipicephalus pulchellus in the east. Except for B. decoloratus, of which more females than males were collected, the numbers of male ticks recovered were equal to or exceeded those of females. Mortality in crossbred dairy cattle caused by heartwater (Cowdria ruminantium infection) was reported during the survey period. An integrated approach to tick control is suggested.

Efficacy of flumethrin 1% pour-on against ticks on cattle under field conditions in Ethiopia.

The efficacy of a flumethrin 1% pour-on (Bayticol, Bayer AH) was evaluated against natural infestations of ticks on cattle on a dairy farm in Ethiopia during 1997/98. The cattle, (n = 92), which were Friesian/ Zebu crosses, were heavily infested with Boophilus decoloratus. Dry cows (n = 8) were randomly selected and allocated either into a treatment or a control group. Flumethrin 1 % pour-on was applied to the treatment group according to the manufacturer's recommendation, i.e. along the dorsal mid-line from the head to the base of the tail. Ticks were counted and identified in situ on treated and control animals. When the total tick counts of the treated group were similar to those on the control, the trial was discontinued. Excellent results were achieved with flumethrin against heavy tick infestations. There was a rapid kill after 24 h post-treatment, and from day 4 onwards 100% control was achieved and maintained for a further 29 days. The results obtained indicate that there was a significant difference between the mean tick counts of the control group compared with those of the treatment group (P < 0,05). The evidence presented here suggests that the flumethrin 1 % pour-on may be applied at 45 day intervals and should provide effective protection against the economically important ticks if it is used at the recommended dosage rate and applied correctly.