Our strategy for eliminating M. hyo from breed-to-wean herds
Photo above courtesy of National Pork Board
By Attila Farkas, DVM
Carthage Veterinary Service, Ltd.
Many pork producers still struggle with Mycoplasma hyopneumonia (M. hyo) in their herds. The pathogen remains one of the prevailing causes of enzootic pneumonia. Even though it’s primarily a chronic respiratory disease of growers, M. hyo can also affect young and adult pigs, especially in recently affected herds.
Most of us in the industry have seen the clinical manifestations of M. hyo disease. There’s usually a persistent, nonproductive cough. Affected herds also have reduced average daily gain, poor feed conversion, high morbidity, low mortality and increased medication cost.
What is it about M. hyo that makes it so costly? M. hyo adheres to the ciliary epithelia in the upper repiratory tract. The result is ciliostasis — the cilia can’t move normally — which interferes with mucin production. This increases the pig’s susceptibility to viral pathogens such as swine influenza virus, as well as bacterial pathogens such as Streptococcus suis, Haemophilus parasuis and others involved in porcine respiratory disease complex.
In a large US production system, the cost of uncomplicated M. hyo infection over a 4-year period has been estimated to be less than US $1 per pig. However, when pigs with M. hyo were co-infected with swine influenza virus or porcine reproductive and respiratory syndrome (PRRS) virus, the economic toll is about $10 per pig.1
Swine veterinarians and producers have attempted to mitigate economic losses from M. hyo with a variety of strategies such as depopulation and repopulation, partial depopulation, whole-herd medication without closure, herd closure and individualized medication — all of which have brought varying degrees of success.
At our practice, we’ve been able to successfully help producers eliminate M. hyo from breed-to-wean herds with the following approach:
- Profile the herd by collecting serum samples from across multiple ages. This helps establish herd-exposure status and prevalence.
- Remove younger animals that have not seroconverted to M. hyo.
- Close the herd to new gilts.
Post herd closure (PHC)
- 1 week PHC — Initiate whole-herd vaccination (boars, sows, gilts and piglets) with a commercial M. hyo bacterin to maximize immunity throughout the population.
- 25 weeks PHC — Vaccinate the sow unit and gilt-developer unit with a commercial M. hyo bacterin.
- 28 weeks PHC — Re‐vaccinate all animals in the sow unit and gilt-developer unit with a commercial M. hyo bacterin to bolster herd immunity.
- 31 weeks PHC — Administer Draxxin® 25 injectable solution (tulathromycin) to all pigs at birth and the pigs aged 1 to 9 days old in the farrowing house. Continue injecting pigs at birth and at 10 days of age with the same injectable Draxxin 25 for 3 consecutive weeks. Draxxin 25 injectable provides therapeutic levels for up to 9 days in lung tissues.2
- 33 weeks PHC — Provide medicated feed to the whole herd. Choose a product with appropriate labeling for M. hyo management, follow label directions and medicate boars, sows and gilts for 3 consecutive weeks. During this period of medicated feed, administer Draxxin injectable solution to sows and boars that are sick or off feed.
- 36 weeks PHC — Collect laryngeal swabs from wean piglets and deep tracheal swabs
from sows and gilts. Test for M. hyo by polymerase chain reaction (PCR). Recommendations on sample size are listed in Table 2.
- 37 weeks PHC — If you have negative M. hyo results by PCR on the laryngeal swabs collected from wean pigs and deep tracheal swabs collected from sows, open the herd to naïve replacement gilts.
- 1 month after the first M. hyo–negative gilts are introduced — Initiate monthly serological testing of replacement gilts. Recommendations on sample size are listed in Table 2.
In 2016, Lucina Galina, DVM, Zoetis, and Maria Clavijo, DVM, University of Minnesota, proposed M. hyo classification criteria for breeding herds (Table 1).3 The purpose of the classification system was to facilitate communication between swine producers, veterinarians, diagnosticians and breeding-stock companies that are evaluating disease-control strategies and to support regional control and elimination efforts,² but we’ve found the system is also a useful tool for measuring M. hyo-elimination success.
It’s important to remember that elimination does not prevent re‐infection. Biosecurity procedures must be kept in place to prevent reccurring infections and the spread of M. hyo and other potential swine pathogens.
Preventive measures can make the difference between success or setbacks in time, money and production. Moreover, to maintain a healthy herd, disease prevention should be an active and ongoing process.
Table 1. M. hyo breeding-herd-status classification criteria*2
|Herd Category||Criteria||Description and Diagnostic Requirements|
|Clinical Signs||Antigen Detection in Respiratory Tract||Serology|
|Yes||Yes||Maybe||Clinical signs consistent with M. hyo are present and M. hyo is detected within lesions and/or in the respiratory tract.
Recently infected populations may be serologically negative.
Untested herds are category I by default.
<10% of weaning-age pigs positive for antigen within respiratory tract
|Yes||M. hyo characteristic clinical signs or lesions are not detected.
At least 90 days of less than 10% of due-to-be-weaned pigs positive by PCR in 4 consecutive samplings of 45 laryngeal swabs at days 0, 30, 60 and 90.*
|No||No||Yes||At least 90 days of negative results from weaning-age pigs by PCR in 4 consecutive samplings of 30 laryngeal swabs at days 0, 30, 60 and 90.*
Herds undergoing M. hyo elimination, no clinical signs or positive tests from respiratory tract of replacement animals, at least 60 days after the initial introduction.
Negative but vaccinated herds are considered category III.
|No||No||No||At least 1 year as category III and have gone through a complete sow rollover. At completion of rollover testing must take place.
Newly established herds and herds that underwent complete depopulation and repopulation.
A minimum of 30 serum samples from sows should test negative by ELISA.*
*http://epitools.ausvet.com/au/content.php?page=PrevalenceSS. Accessed December 2015.
Table 2. Recommended number of diagnostic samples based on population size
|Population Size Required to Detect|
*All calculations assume a 5% confidence (Z beta error)
IMPORTANT SAFETY INFORMATION: Withdraw DRAXXIN/DRAXXIN 25 five (5) days prior to slaughter. Do not use in animals known to be hypersensitive to the product.
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1. Haden CD, et al. Assessing production parameters and economic impact of swine influenza, PRRS, and Mycoplasma hyopneumoniae on finishing pigs in a large production system. Proc AASV. Denver, Colorado. 2012;75‐76
2. Senn MK, et al. Evaluation of DRAXXIN® Injectable Solution for the control of swine respiratory disease. AASV. 2010;143-146
3. Galina L, Clavijo MJ. Establishing Mycoplasma hyopneumoniae herd status classification criteria for breeding herds. AASV. 2016;167‐169