MYCOPLASMAL MASTITIS IN DAIRY CATTLE

July 20, 2020

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MYCOPLASMAL MASTITIS IN DAIRY CATTLE

Bovine mastitis is recognized as one of the most costly diseases in dairy cattle across the world. It has been estimated that bovine mastitis reduces milk yield by approximately 21% in infected cattle herd. Infl ammation of the udder, or mastitis, is commonly observed in cattle and buffaloes due to their anatomical predisposition, especially during the peripartum period.

Mycoplasma Mastitis———

Mycoplasma species are very small bacteria and are unique because they lack a bacterial cell wall. This means they are neither Gram-negative nor Grampositive. Several Mycoplasma species cause mastitis, including M. bovis (most common mastitis isolate), M. alkalescens, M. bovigenitalium, and M. canadense. These organisms may be isolated from both sick and healthy animals, from the respiratory and reproductive tracts and other sites.
Mastitis is a well-recognized and costly disease of dairy cattle. Most farmers are well acquainted with traditional causes of mastitis such as Staphylococcus aureus and Streptococcus agalactia. The widespread adoption of standard mastitis control practices such as teat dipping, dry cow therapy, appropriate treatment, judicious culling and good milking preparation has allowed many dairy farmers to control contagious forms of mastitis.

What is Mycoplasma?

Mycoplasmas are a group of very small organisms that can be cultured from multiple body sites of both sick and healthy cattle. Some common species of mycoplasma include M. bovis (most commonly cultured from the udder), M. alkalescens (commonly cultured from the respiratory tract, M. bovigenitalium (commonly cultured from reproductive tract) and M. canadense (commonly cultured from joints)

Species of Mycoplasma

There are several species of Mycoplasma capable of causing cattle infections. They may cause pulmonary infections, middle ear infections, joint infections etc. Some, but not all species are also capable of causing mastitis. It is quite common for these other symptoms of Mycoplasma infectionj to be noted at the same time as mastitis problems are occurring.
When attempting to identify and resolve Mycoplasma problems, it is always beneficial to understand the organism involved. Other considerations include; how to spot problems, how to treat infections, risks to the overall herd, and how to minimize these risks.
Since Mycoplasma are unique organisms, it is especially important to determine if they are the cause of a mastitis problem. To date there is no effective tool for treating a Mycoplasma mastitis problem, so other control techniques have to be implemented.
Species of Mycoplasma-causing mastitis
There are several Mycoplasma species that may be involved with mastitis, but certain ones are more of an issue than others. The following list identifies potentially infectious species and their basic characteristics.

1. Mycoplasma bovis – the most common cause of Mycoplasma mastitis. Estimated it is responsible for about 50% or more of the cases of mastitis caused by Mycoplasma. Mycoplasma bovis is a bacterium that, while not harmful to humans, causes illness in cattle, such as mastitis, pneumonia and arthritis. Because of its structure, the bacterium is unaffected by many antibiotics, which makes it a difficult disease to treat. And because the symptoms shown by infected animals are similar to other diseases, it is problematic to detect.
2. Mycoplasma bovigenitalium – found in reproductive tract of animals, may contaminate the teats when uterine discharges occur.
3. Mycoplasma canadense – occasional cause of mastitis and quite resistant to heat treatment.
4. Mycoplasma californicum – may cause mastitis
5. Mycoplasma alkalescens – may cause mastitis
6. There are several other species of Mycoplasma that may cause disease but they are not considered to be a significant cause of mastitis.

What Does Mycoplasma Mastitis Look Like?

The classic symptoms of mycoplasma mastitis :
• Multiple quarters involved • Dramatically decreased milk production • Cows appear otherwise healthy but have severe mastitis • Milk has sandy or flaky sediments in watery or serous fluid However, cows can develop subclinical infections with mycoplasma and have normal appearing milk.1 These subclinically infected cows may have intermittent periods of abnormal milk or their milk may continually appear normal. Somatic cell counts of subclinically infected cows will be increased. Cows that have had mycoplasma cultured from their milk should be considered to be permanently infected regardless of the visual appearance of their milk.

Transmission-——–
Mycoplasma is a contagious pathogen, and thus is transmitted cow-to-cow through infected milk on milking equipment or milker’s hands. New herd infections occur primarily by the introduction of new, infected animals. However, new infections may occur without the introduction of new infected animals. It has been reported that clinical mastitis cases occurred after contact with adult cows showing respiratory symptoms, and after contact with calves infected with Mycoplasma pneumonia or arthritis. Heifers may also become infected with Mycoplasma prior to calving and serve as subclinical carriers after freshening. Mycoplasma is unique in that it may also be spread hematogenously (through the blood), meaning that an animal with a respiratory infection caused by Mycoplasma may also develop Mycoplasma mastitis. These bacteria can be shed in large numbers in the milk of infected animals. Because of this, the hospital parlor is a major source of infection during an outbreak, resulting in many new infections in a short period of time. Since Mycoplasma is not susceptible to intramammary antibiotics, treatment may actually spread the bacteria if workers hands or infusion equipment become contaminated with milk from an infected cow.

Infection-————

The characteristic presentation of Mycoplasma mastitis is multiple quarters affected, severely decreased milk production, watery or serous milk with flakes, and the cow appears healthy. Clinical mastitis cases that fail to respond to therapy and from which no bacteria can be isolated using traditional aerobic culture techniques should also be suspect for Mycoplasma. Some cows infected with Mycoplasma may be subclinical. The somatic cell count of affected cows is usually elevated, but may also be normal.

Risk Factors———-
Significant risk factors for Mycoplasma mastitis include: the purchase of new, untested animals; poor housing ventilation; contact between calves and adult cattle; and poor hygiene practices in the milking parlor.

Diagnosis———-

Mycoplasma may be diagnosed either with bulk tank culture, or individual cow culture. However, in order to isolate Mycoplasma in the laboratory special culture media and incubation conditions must be employed. This means that Mycoplasma will not be identified by on-farm culture, and Mycoplasma culture must be specifically requested from the diagnostic lab.

Control ———-

There is no treatment for Mycoplasma mastitis and once infected, cows should be considered infected for life. The only means of control is identification, segregation and culling. In cases where a large percentage of the herd is affected and immediate culling is not feasible, identification and segregation of affected animals must occur with care taken to limit opportunities for transmission. Affected animals must be milked last and milking equipment thoroughly disinfected between milkings. Excellent hygiene practices are required to avoid transmitting Mycoplasma in the milking parlor. Herds that routinely purchase new animals should have their bulk tank milk tested regularly for Mycoplasma, and should request a bulk tank culture from the source herd.

How can Mycoplasma be Controlled?

The first step in controlling mycoplasma mastitis is recognizing that the disease is present in dairy herds. A strong association between the introduction of new cattle and outbreaks of mycoplasma mastitis has been reported.1 Mastitis biosecurity programs can be used to decrease the risk of purchasing infected cattle. Bulk tank cultures from the herd of origin should be requested for non-lactating purchased cows and somatic cell counts and composite milk samples from individual cows should be reviewed prior to purchasing lactating cows. Cows that calve after purchase should be isolated until a negative composite milk sample is obtained. Herds that are routinely purchasing cattle should submit bulk tank milk for mycoplasma twice monthly. The management of sick and fresh cows also contribute to the spread of this organism. Fresh cows should not be housed in the same pens or milked with the same equipment as sick cows. The feeding of waste milk to calves is another source of transmission of this disease throughout the herd. Calves fed infected milk may develop pneumonia, joint infections and head tilts related to ear infections.1 When mycoplasma is found in a bulk tank or individual cow culture, the number of infected cows must be determined. Depending upon herd size, there are several strategies that can be considered. If resources allow or the herd is small, composite samples from all cows should be submitted for culture. In larger herds, group milk samples can be submitted by sequentially culturing the bulk tank during milking. Individual milk samples can be obtained from cows only in the infected groups. There is no treatment for cows that develop mycoplasma mastitis. Antibiotics are totally ineffective for this organism. Cows that are infected with mycoplasma should always be considered as infectious, regardless of their production level, appearance of their milk or subsequent negative milk culture. In most cases, infected cows should be promptly culled. The only exception to this rule is when a culling is financially unacceptable because a large proportion of a herd is infected. In this case a herd specific strict segregation plan should be developed.

Infection Control

No effective treatment exists for Mycoplasma mastitis. Instead, dairies should focus on disease control through routine sampling of milk specimens and screening of all animals at freshening. For large herds, composite sampling of the bulk tank should occur after each production group, allowing owners to identify infected groups and cows. After an infection has been identified, best practice includes monitoring the bulk tank milk weekly until all cows (including those that were pregnant or dry during the outbreak) calve. Dairies should also:
• Isolate Mycoplasma positive animals from the herd.
• Employ good milking hygiene practices for infected and suspect cows: rubber gloves and hand disinfection between animals; pre-milking teat disinfection (iodine 0.5 to 1%) and post-milking teat dipping; dedicated milking unit for affected animals.
• Avoid barn overcrowding and ensure good barn sanitation practices, especially during calving.
• Exercise caution during animal replacement: screen individual cows before introduction into the existing herd and the bulk tank when purchasing an intact herd.
Owners should consider culling, depending on several variables (type of infection- subclinical/clinical/chronic, available facilities, number of infected cows, milk production levels, reproductive statuses, and replacement options). This decision is largely dairy-specific and ranges from culling all infected animals to only culling those that demonstrate chronic clinical infection.

Treatment

Mycoplasma is very difficult to treat in calves as well. Several of the commonly used antibiotics do not work well for Mycoplasma. Penicillin kill bacteria by destroying their cell walls. Since Mycoplasma does not have a normal cell wall, these antibiotics are ineffective in treating the organism.
Oxytetracycline has produced mixed results in treating Mycoplasma in calves. The two most important factors in the successful treatment of Mycoplasma infected calves are early recognition and prolonged treatment. Calves that are treated early in the course of the disease respond fairly well, but need to be treated for 10 to 14 days or 50 percent to 70 percent will relapse and require treatment again. Each time a calf relapses it will have more lung damage and be less likely to recover. Ear infections also need to be treated for a longer period of time. If problems with Mycoplasma are suspected, it is critical that you work with a veterinarian to develop a treatment protocol that will fit these guidelines and best meet the needs of your farm. Using antibiotics to treat swollen joints is usually unrewarding as long as the calves no longer have pneumonia. The most effective treatment for these calves is to provide easy access to feed and water so they will not starve or dehydrate. It may also be necessary to run these animals to feed and water several times a day until they have begun to recover. The most fortunate aspect of this disease is that it appears that a large number of these calves will recover if given enough time. It can take months for the joints to fully recover and the cattle to start gaining weight.