Mycoplasma otitis in California calves

Transcription

1 J Vet Diagn Invest 6: (24) Mycoplasma otitis in California calves Catherine G. Lamm, Linda Munson, Mark C. Thurmond, Bradd C. Barr, Lisle W. George Abstract. A retrospective study of Mycoplasma otitis in California calves submitted for necropsy between 993 and 22 was conducted to characterize the demographic features of the disease and the pathologic findings associated with infection. Sixty-one confirmed cases of Mycoplasma otitis were identified among 2,525 necropsied cattle. All affected animals were calves, ranging in age from 2 weeks to 4 months and with a median age of.5 months. Ninety-two percent of the cases were dairy breeds. A higher percent of necropsied calves with Mycoplasma otitis were males (.45%) than females (.23%). The proportion of cases that had Mycoplasma otitis increased from 993 to 22, and there was a significant (P.5) seasonal distribution, with the highest proportion in the spring and the lowest in the summer months. Infections involved both the middle and inner ear and were characterized by a suppurative inflammatory response with extensive bony involvement. Three species of Mycoplasma were isolated from the ears: M. bovis, M. bovirhinis, and M. alkalescens. Concurrent pneumonia occurred in 47 cases (77%), and Mycoplasma was isolated from the lungs of 3 of those cases. The increasing proportion of Mycoplasma otitis cases in the past years emphasizes the importance of identifying risk factors that could be modified to lower the incidence of this disease in calves. Introduction Otitis is a rare clinical disease in calves that manifests as head tilt and facial paralysis due to involvement of cranial nerve VII, cranial nerve VIII, and peripheral vestibular structures. 6 In study, Mycoplasma bovis was the most common agent isolated from dairy calves with otitis, in contrast to pigs, sheep, and pasture-raised cattle in which otitis is primarily caused by Pasteurella.,4,7,2 Mycoplasma bovis is of the more economically important species of Mycoplasma, causing not only otitis but pneumonia and arthritis in calves, as well as a highly infectious mastitis in dairy cattle.,3,9,2 Mycoplasma bovirhinis and M. alkalescens also have been isolated from cows with mastitis. Infected milk may be the source of Mycoplasma in calves with otitis because nasal colonization was more prevalent in calves from herds with Mycoplasma mastitis than without Mycoplasma mastitis. 2 Risk factors, transmission, and pathogenesis of M. bovis ear infections have not been well characterized for any species. To date, only study has reported M. bovis otitis media, and that was in 5 calves originating from a single farm in Michigan. 2 The features of the disease in a larger population have not been described. In California, middle-ear infections caused by M. bovis have been recognized by practitioners who believe the Department of Veterinary Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, CA 956 (Lamm, Munson, Barr), and Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 956 (Thurmond, George). Corresponding Author: Linda Munson, Department of Veterinary Pathology, Microbiology, and Immunology, University of California, Shields Avenue, Davis, CA 956. incidence is increasing. The objective of this study was to characterize the clinical signs, epidemiology, and pathologic features of Mycoplasma otitis in California calves submitted over a -year period to the Veterinary Medical Teaching Hospital (VMTH) at the University of California, Davis, or to the laboratories within the California Animal Health and Food Safety Laboratory System (CAHFS). Materials and methods Study population. Necropsy reports were reviewed for 2,525 cattle submitted to the VMTH and CAHFS pathology laboratories from 993 through 22. For an animal to be included in the study, it had to be a domestic bovid of any age with otitis confirmed by pathology and with Mycoplasma cultured from the ear at necropsy. Data. Data obtained for each affected animal included age, sex, breed, month of submission, year of submission, herd type, and geographic location. Calves less than 4 wk of age were categorized as less than mo old. If the age of the calf was reported in days, the age was rounded to the nearest half month. Because some herds submitted multiple cases, selected data were analyzed on a herd basis rather than on an individual animal basis, so that these herds were not overrepresented. Clinical descriptions and management factors, including a history of Mycoplasma mastitis in the herd, type of milk fed to calves, and type of housing, were acquired from histories recorded on submission forms or by interview with clinicians. Further in-depth information about management practices was not available. Histologic slides of the ear lesions from 6 cases were available for review. Bacteriologic culture results were complied for each case. Mycoplasma species were cultured on Mycoplasma N plates or in Mycoplasma D Broth tubes. In- 397

2 398 Lamm et al. Table. Percent categorized by breed and sex of California cattle necropsied between 993 and 22 that had Mycoplasma otitis. Figure. Age distribution of 57 California calves with Mycoplasma otitis. Age was not available for 4 of the calves. direct immunoperoxidase staining was used to serotype the species of Mycoplasma isolated. Laboratory results were complied for each case, including polymerase chain reaction for bovine virus diarrhea virus (BVDV), fluorescent antibody tests for BVDV, infectious bovine rhinotracheitis virus (IBRV), bovine respiratory syncytia virus and parainfluenza 3 virus, as well as immunohistochemical staining for IBRV and BVDV. Descriptive statistics were calculated for all numerical data. The total number of cattle submitted for necropsy, independent of final diagnosis, was calculated for each sex, breed, month, and year. These values were used as denominators to calculate the proportions of cattle with Mycoplasma otitis for each factor examined. Chi-square analysis was used to test the null hypothesis that the occurrence of Mycoplasma otitis was independent of sex. The Freedman test for seasonality was used to assess a possible seasonal trend in the monthly proportion of animals submitted with Mycoplasma otitis. 5 Linear regression was used to estimate a secular trend in the annual proportion of animals submitted with Mycoplasma otitis during the -yr period. The coefficient of determination (R 2 ) was calculated to estimate the amount of variation in the proportion of submissions that was attributable to year-to-year variation. 7 Results Demographics. In the -year study period, there were affected animals that met the case inclusion criteria, submitted to 4 laboratories (VMTH, CAHFS Davis, CAHFS Tulare, and CAHFS San Bernadino). These cases were presented on 4 occasions from 32 different herds, with 6 animals submitted from a single herd at a given time. The 32 herds submitting cases were located generally around the 4 diagnostic laboratories. The age range of cases was 2 weeks 4 months, with 77% (47/) of affected calves being 2 months old or less (Fig. ). The mean age was.49. month, and median age was.5 months. The majority (92%) of affected calves were dairy breeds (Table ). Although equal numbers of males and females were affected, a significantly higher percent of male calves had Mycoplasma otitis (.45%) than female Trait Breed Angus Brown Swiss Holstein Jersey Mixed Sex Male Female Unknown Percent of necropsied calves by trait*.6 (/637).34 (3/29).34 (46/3,583).62 (7/,29).8 (4/4,773).45 (24/5,357).23 (24/,639).6 (3/2,238) Percent of otitis calves by trait.5 (/) 5 (3/) 75.5 (46/).5 (7/) 6.5 (4/) 39.3 (24/) 39.3 (24/) 2.3 (3/) * Numerator is the number of Mycoplasma cases and denominator is the total number of animals submitted for necropsy for the category. Numerator is the number of Mycoplasma cases and denominator is the total number of Mycoplasma calves identified. The proportion of males was significantly greater than for females. Odds ratio.99 (95% confidence limits.9, 3.63); 2 5.7, P.23. calves (.23%) (P.23) because twice as many females were necropsied (Table ). The Freedman test for seasonality identified a significant seasonal trend in the proportion of animals submitted with Mycoplasma otitis (Fig. 2, P.5). The proportion of cases with Mycoplasma otitis was highest in March and lowest in July. The mean number of cases per month was , and median number of cases was 4. The proportion of annual cases with Mycoplasma otitis increased significantly during the -year period (Fig. 3, P.4, R 2.66). The number of cases Figure 2. Monthly distribution of calves with Mycoplasma otitis and the proportion of animals necropsied that had Mycoplasma otitis. A significant seasonal trend existed for the monthly proportion of necropsied calves with Mycoplasma otitis (P.5).

3 Mycoplasma otitis in calves 399 Table 2. Gross pathologic findings in the ears and other organs of calves with Mycoplasma otitis. These data are based on the certainty that all portions of the ear were examined. Figure 3. Ten-year secular trend of Mycoplasma otitis in calves submitted for necropsy between 993 and 22 in California. A significant increasing linear trend existed for the proportion of annual calves with Mycoplasma otitis. Regression equation: proportion of calves year, (P.4, R 2.66). Lesion distribution Otitis Media Interna Media and interna Media and externa Media, interna, and externa Both ears affected Right ear affected Left ear affected Unknown side(s) affected Pneumonia Arthritis Meningitis Number examined 4 29 * Values given within parentheses are in percent. Number with lesion* 36 (59) 4 (6.6) 7 (27.9) 3 (4.9) (.6) 46 (75.4) 5 (8.2) 7 (.5) 3 (4.9) 47 (77) 4 (29) 5 (7) of Mycoplasma otitis increased from zero in 996 to 8 cases in 22, with no affected animals reported before 994. The mean number of cases per year was , and the median number was 5. The trend in the number of cases is compared with annual rainfall data available from the National Weather Service (Fig. 4). Management practices. Twenty-four of the 32 herds (75%; representing 36 cases) were dairies that raised their calves on site, and 8 of 32 herds (25%; representing 25 cases) were from calf-raising operations located separately from dairy herds. Of the 4 herds for which the type of milk fed to calves was available, 5% (7/4) fed nonheat-treated milk, 4% (2/4) fed milk replacer, and 36% (5/4) fed heat-treated, bulktank or hospital milk. A history of previous Mycoplasma infections was reported for herds. Thirtytwo herds did not report whether or not Mycoplasma infections had been diagnosed previously. Clinical history. Head tilt, ear infection, or facial nerve paralysis was listed in the clinical history for 64% (39/) of affected animals and pneumonia for 5% (9/) of the cases. Other neurological signs included cranial nerve VIII deficits, twitching, and/or incoordination. Depression or ill thrift was reported for 3% (8/) of affected animals. Diarrhea was reported for case, swollen joints for 3 cases, and unexplained death for case. Pathology. Gross lesions described in necropsy reports of the calves with Mycoplasma otitis are summarized in Table 2. The most common reported aural lesion was bilateral otitis affecting the middle ear. Affected ears were commonly filled with caseous or suppurative exudate (Fig. 5). Bones surrounding the infected ears were often soft or irregularly shaped or both. The tympanic bulla was perforated in case. Figure 4. Comparison of -year secular trend of Mycoplasma otitis with annual rainfall in California as recorded by the National Weather Service. Figure 5. Skull of a calf with Mycoplasma otitis with the tympanic bulla opened. The ear canal is filled with caseous exudates and inflammatory changes extend into the surrounding bones (arrow).

4 4 Lamm et al. Figure 6. Middle ear and adjacent bone from a calf with Mycoplasma otitis. Abundant inflammatory cells and necrotic debris fill the auditory tube (asterisk), efface the epithelium (arrow), and extend into the surrounding soft tissues and bone. HE 2.5. Pneumonia was a common concurrent finding. Arthritis and meningitis were also noted in 4 and 5 cases, respectively. By histology, the ear lesions consisted of extensive inflammatory infiltrates that filled all auditory tubes and ducts and obliterated normal architecture (Figs. 6, 7). In most cases, all middle- and inner-ear structures were involved. Infiltrates consisted predominantly of neutrophils admixed with abundant fibrin and necrotic debris. The epithelium lining the middle- and innerear canals was commonly effaced or had undergone squamous metaplasia. The underlying connective tissue was extensively infiltrated with neutrophils, plasma cells, and macrophages. In some areas, there was abundant fibroplasia with granulation tissue formation. In most sections, the intense inflammation extended deeply into adjacent bones inciting osteoclastic resorption and new bone formation (remodeling). A 3- month-old Holstein male with M. bovirhinis infection had less severe inflammation and structural damage than calves with M. bovis otitis and had only mild fibrinosuppurative exudates in the tubes of the ear. Bacteriology and virology. Ear culture results are summarized in Table 3. Mycoplasma bovis was the most common species of Mycoplasma isolated from the ear (5/ or 84% of the cases). Mycoplasma bovirhinis was isolated from 2% (/) of the affected calves and M. alkalescens was isolated from the ears of 3% (2/) of the cases. The Mycoplasma isolated from the ears of % (7/) of the calves was not speciated. Bacterial cultures of the lung were performed in Figure 7. Middle ear and surrounding bone from a calf with Mycoplasma otitis. Extensive neutrophilic infiltrates and necrotic debris are associated with mucosal ulceration, squamous metaplasia (arrow), and underlying bone with bony remodeling (asterisk). HE. 87% (53/) of the cases. The lungs were cultured from 47 calves with pneumonia and 6 calves without pneumonia. Lung culture results are summarized in Table 3. Mycoplasma sp. were the only organisms isolated from both the ear and the lung of 25% (3/53) of the cases with lung cultures, and all of these cases had pneumonia. Mycoplasma sp. were not isolated from the lungs of 43% (23/53) of the cases cultured. The joints of 2 of the 4 cases with arthritis were cultured, and was positive for Mycoplasma sp. Two additional cases had Mycoplasma sp. cultured from the joints. Of the 5 cases with meningitis, only was cultured, and Salmonella was isolated. One case without meningitis had the brain cultured and tested positive for Mycoplasma sp. Only case was positive for BVDV in the lung and kidney, and case was positive for IBRV in the intestines. Table 3. Bacteria isolated from California calves with Mycoplasma otitis. Bacteria cultured* Ear Lung Mycoplasma Mycoplasma and Arcanobacterium Mycoplasma and Pasteurella Mycoplasma and other bacteria Coliforms Pasteurella Arcanobacterium Streptococcus Proteus Other mixed bacteria No bacteria Total 53 * For each bacteria type/classification the number of positive cultures is not necessarily from the same calf.

5 Mycoplasma otitis in calves 4 Discussion This study found a significant increase in the rate of Mycoplasma otitis diagnosed between 993 and 22, mainly affecting - to 2-month-old, male dairy calves. The possibility that rainfall played a role in the increased incidence of disease was explored by reviewing the total annual rainfall in California from 993 to 22 from the National Weather Service records. A dramatic increasing trend in the annual rainfall was not seen during these years and did not parallel the increased number of Mycoplasma otitis cases. This upward annual trend may be related to the perceived increase in Mycoplasma mastitis on dairies or to higher rates of clinical disease due to the emergence of a more pathogenic strain of Mycoplasma. It is also possible that an increased awareness of the disease has ultimately resulted in more submissions of affected animals. The high occurrence of disease in calves less than 2 months of age coincides with the period when calves are fed milk or milk replacer and are housed in close contact. The increased proportion observed in younger animals could be because of transmission between calves in adjacent hutches or transmission through infected milk. The 2-fold higher proportion of Mycoplasma otitis in males compared with females in the present study suggests males are at a higher risk than females. It is possible that males are predisposed to infection because they are often fed poorer quality milk and not colostrum and may receive less veterinary care than female calves. There was a seasonal trend to otitis, with more cases occurring during late winter and spring. Mycoplasma mastitis has been thought to be seasonal in California with a similar high prevalence in the rainy season (Jan through May). The parallel between the seasonal trend of Mycoplasma mastitis and Mycoplasma otitis suggest some connection, possibly through the feeding of infected milk. Other viral and bacterial infections also may be more common during this season, and perhaps previous infections with these agents predisposed the calves to secondary Mycoplasma infections acquired through milk. However, there was little evidence to suggest that Mycoplasma was an opportunist subsequent to viral infection in the current study, in contrast to other species. 2 Because Mycoplasmas were the only organisms isolated from the ears of most calves, it would appear that Mycoplasma infection alone can cause this disease. The present study identified 2 other species, M. bovirhinis and M. alkalescens, not previously isolated from animals with otitis. Mycoplasma alkalescens is associated with mastitis and arthritis in cattle. 9 Mycoplasma bovirhinis is considered an opportunist in respiratory infections and is occasionally found in the milk of cattle with a milder form of mastitis. 8,9,6 It is not known whether these 2 species of Mycoplasma were primary pathogens or secondary opportunists in the 3 affected animals because other bacteria were isolated from either the ear or the lung. Interestingly, the single case with otitis from which M. bovirhinis was isolated had considerably less severe lesions in the ear than calves with M. bovis. Whether this milder inflammation can be attributed to the less pathogenic species of Mycoplasma isolated or to the duration of disease in this case could not be determined. The pathogenesis of Mycoplasma otitis remains unknown. Infection could result through direct extension from the external ear, from the oropharynx, or less likely, through blood-borne infection as is seen with other species. 2,3,4,5,7 Experimental studies are needed to determine the route of entry of Mycoplasma and whether this infection is primary or secondary to other infections. The transmission of Mycoplasma to calves with otitis has yet to be identified. In rats with otitis, Mycoplasma is most commonly transmitted through respiratory secretions. 3,5 In feedlot calves with pneumonia and arthritis, direct nose-to-nose transmission of M. bovis has been suggested. On the basis of knowledge of transmission of Mycoplasma sp. in other host species, possibilities for transmission include direct or indirect contact with respiratory secretions as well as the feeding of infected milk. 4,2,3,4,5,7,2 It is interesting to note that, in a previous study, M. bovis was isolated from the upper respiratory tracts of randomly-selected calves 4-months old, similar to the age range of affected calves in the current study. 2 A higher prevalence of M. bovis nasal infection was found in calves fed milk from cows with Mycoplasma mastitis. 2 These observations suggest that the feeding of infected milk may play a role in transmission. In addition, 2 of the Mycoplasma species (M. bovis and M. alkalescens) isolated from 98% (6/) of cases in this study can cause mastitis in cattle and can be shed in the milk. 3,9 In goats, feeding milk from does with Mycoplasma mastitis has been associated with Mycoplasma arthritis in kids. 4 This mode of transmission may also occur in calves that develop subsequent otitis. It was not possible in the present study to link feeding Mycoplasma-contaminated milk with the development of otitis because complete histories were not available. The route of infection in calves with Mycoplasma otitis needs to be further investigated, with special attention to transmission through feeding Mycoplasma-contaminated milk. The clinical presentation of Mycoplasma otitis as head tilt and neurologic signs in the present study is similar to that reported in the Michigan study. 2 The present study also identified similar concurrent path-

6 42 Lamm et al. ologic findings, including pneumonia, arthritis, and meningitis as reported in previous studies of Mycoplasma infection. 8,2 Possibly, Mycoplasma is a more common cause of meningitis in calves than previously suspected. Further histologic examination and bacterial culture of the brain and cranial nerves of calves with otitis needs to be performed to determine if neural involvement is common. In summary, this study found the annual proportion of Mycoplasma otitis in California calves submitted to necropsy increased significantly in the past years. The seasonality of otitis closely paralleled the fluctuation in the incidence of Mycoplasma mastitis observed by practitioners. Therefore, feeding of infected milk to the calves is of the more likely modes of transmission. The higher risk associated with young, male dairy calves suggests that management practices that differ between sexes and that are specific to this age group may play a role in the development of Mycoplasma otitis. Acknowledgements The authors thank Dr. Deryck Read for contributing cases and slides for review and Larry Crawford for assistance with computer searches. The authors also thank the following pathologists and pathology residents for contributing cases: Drs. John M. Adaska, Lucy Anthenill, Patricia C. Blanchard, Barbara M. Daft, Cynthia A. Farman, Lisa LaFranco- Scheuch, Hailu Kinde, M. Kevin Keel, Robert B. Moeller, Janet Moore, F. Chuck Mohr, Judith A. St. Leger, and Dennis W.Wilson. The authors also thank Dr. Richard Walker for his information on culturing Mycoplasma. The authors also thank the clinicians and clinical residents who managed the cases before submission, as well as Drs. Edward Henry, Ken Mitchell, Dale Moore, Michael Overton, and James Reynolds. References. Adegboye DS, Halbur P, Nutsch R: 996, Mycoplasma bovisassociated pneumonia and arthritis complicated with pyogranulomatous tenosynovitis in calves. J Am Vet Med Assoc 29: Bennett R, Jasper D: 977, Nasal prevalence of Mycoplasma bovis and IHA titers in young dairy animals. Cornell Vet 67: Culler JS, Tyler JW: 996, Mammary gland health and disorders. In: Large animal internal medicine, ed. Smith BP, pp. 9. Mosby-Year Book Inc., St. Louis, MO. 4. East NE, DaMassa AJ, Logan LL: 983, Milkborne outbreak of Mycoplasma mycoides subspecies mycoides infection in a commercial goat dairy. J Am Vet Med Assoc 82: Freedman LS: 979, The use of Kolmogorov-Smirnov type statistic in testing hypotheses about seasonal variation. J Epidemiol Community Health 33: George LW: 996, Diseases of the nervous system. In: Large animal internal medicine, ed. Smith BP, pp. 3, Mosby-Year Book Inc., St. Louis, MO. 7. Hosmer DW, Lemeshow S: 2, Applied logistical regression. John Wiley and Sons, New York, NY. 8. Jasper D: 979, Bovine mycoplasmal mastitis. J Am Vet Med Assoc 75: Jasper D: 98, Bovine mycoplasmal mastitis. Adv Vet Sci Comp Med 25: Jasper D, Dellinger J, Rollins M: 979, Prevalence of Mycoplasma bovine mastitis in California. Am J Vet Res 4: Jensen R, Maki LR, Lauerman LH: 983, Cause and pathogenesis of middle ear infection in young feedlot cattle. J Am Vet Med Assoc 82: Klein J: 979, Epidemiology, microbiology, and management of otitis media. Pediatrician 2: Kohn DF, Kirk BE: 969, Pathogenicity of Mycoplasma pulmonis in laboratory rats. Lab Anim Sci 9: Macleod NSW, Wiener G, Barlow RM: 972, Factors involved in middle ear infection (otitis media) in lambs. Vet Rec 9: Percy D, Barthold S: 993, Pathology of laboratory rodents and rabbits. Iowa State University Press, Ames, IA. 6. Petterson B, Uhlen M, Johansson K: 996, Phylogeny of some Mycoplasmas from ruminants based on 6S rrna sequences and definition of a new cluster within the hominis group. Int J Syst Bacteriol 46: Shimada A, Adachi T, Umemura T: 992, A pathologic and bateriologic study on otitis media in swine. Vet Pathol 29: Stipkovits L, Glavits RM: 993, Mycoplasmal arthritis and meningitis in calves. Acta Vet Hung 4: Walker R: 999, Mollicutes. In: Veterinary microbiology, ed. Hirsh DC, pp Blackwell Sciences, Inc., Malden, MA. 2. Walz P, Mullaney T, Render J: 997, Otitis media in preweaned Holstein dairy calves in Michigan due to Mycoplasma bovis. J Vet Diagn Invest 9: