Inbound survival rate and observed symptoms
Eighty-two dogs flew overseas during the study period to undergo MVR in Japan from September 2017 to March 2019. All dogs were in the passenger cabin during the flight. Two dogs were excluded from the study because they underwent a second MVR. The numbers of dogs were as follows: Chihuahua 14, Maltese 14, Cavalier King Charles Spaniel 10, Mixed breed 10, Shih Tzu 9, Miniature Schnauzer 4, Toy Poodle 3, Yorkshire Terrier 3, Papillon 2, Pomeranian 2, American Eskimo 1, Bichon Frise 1, Beagle 1, Chinese Crested Dog 1, Dachshund 1, Havanese 1, Pekingese 1, and Spitz 1. The characteristics of the dogs, grouped by departure region, are summarized in Table 1.
Table 1
Profile of dogs grouped by regions of their destination. The Shapiro–Wilk test was used to confirm normal distribution. p ≧ 0.05 was considered a normal distribution.
|
Asia
|
Americas
|
Europe
|
All
|
Flight hours
|
1.5–5
|
7.5–21
|
11–17
|
–
|
Number of dogs
|
19
|
57
|
4
|
80
|
Age (years)
|
9.6 ± 1.5
|
1.0 ± 1.9
|
9.7 ± 1.5
|
9.9 ± 1.8
|
Body weight (kg)
|
3.8 ± 1.2
|
5.5 (2.3–15.0)
|
7.9 ± 7.3
|
5.1 (2.1–18.6)
|
Sex,
male/female [%]
|
16/3
[84.2/15.8]
|
36/21
[63.2/36.8]
|
3/1
[75/25]
|
55/25
[69/31]
|
ACVIM*
B1/B2/C/D [%]
|
1/7/9/2
[5.3/36.8/47.4/10.5]
|
1/24/25/7
[1.8/42.1/43.9/12.3]
|
0/1/3/0
[0/25/75/0]
|
2/32/37/9
[2.5/40/46.3/11.3]
|
*ACVIM, classification based on Consensus Statements of the American College of Veterinary Internal Medicine (ACVIM) for myxomatous mitral valve disease in dogs: https://onlinelibrary.wiley.com/doi/10.1111/jvim.15488 |
On arrival in Japan, four dogs showed severe symptoms related to heart failure. Three dogs were diagnosed with pulmonary edema, and one with left atrial rupture. After receiving treatment, two dogs with pulmonary edema recovered, and two dogs died; thus, the overall survival rate for the inbound journey was 97.5%. The dog that died of pulmonary edema was a 7-year-old Cavalier King Charles Spaniel that flew from eastern USA (total flight hour, 12 h). The dog that died of left atrial rupture was a 9-year-old Maltese that flew from western USA (total flight hour, 11 h).
The conditions of the dogs during the journey were reported through an arbitrary questionnaire administered to owners. Of the 80 dogs included in this study, 46 completed the questionnaires. Of the 46 dogs, 47.8% (22) of the dogs showed decreased activity levels before air travel (Fig. 1). Two of these dogs reported a further decrease in activity during the flight. In addition, two dogs with normal activity levels before air travel were reported to have decreased activity during the journey. A reduction in appetite was reported in 6.5% (three) of the dogs before the flight, but these dogs were stable during the journey (Fig. 2). In contrast, of the 43 dogs that had a normal appetite before the air travel, eight dogs showed a decrease in appetite during the journey. Cough and dyspnea were monitored during the journey. Cough was observed in 47.8% (22) of the dogs before the flight (Fig. 3). Of these dogs, 86.4% showed stable status during the journey. Two dogs showed exacerbation of coughing only during the flight, and one dog that developed pulmonary edema showed persistent coughing after arrival. Of the 24 dogs that had no coughing symptoms before the flight, one dog was observed with the symptoms only during the flight, and three dogs showed persistent coughing after the flight (including one dog with pulmonary edema). Regarding dyspnea, 28.3% (13) of the dogs had symptoms prior to the flight (Fig. 4). Of these dogs, 61.5% had stable respiratory status during the journey. Four dogs showed exacerbation of dyspnea only during the journey, and one dog that developed pulmonary edema showed persistent symptoms after arrival. Among the 33 dogs with normal breathing status before the flight, 11 were reported to have dyspnea observed only during the flight (including one dog with pulmonary edema) and five dogs were reported to have persistent breathing problems after arrival (including two dogs with pulmonary edema). Digestive symptoms, such as vomiting and diarrhea, were not reported during the flight.
Surgical survival rate and hospitalization period
Of the 80 dogs in this study, five did not undergo MVR. The reasons were death of two dogs after arrival, unfavorable preoperative screening results, or refusal of consent to surgery by the owner. Three of the 75 dogs that underwent MVR died postoperatively; thus, the surgical survival rate was 96%. In comparison, the surgical survival rate in 629 domestic dogs during the same study period at this facility was 94.3%. The average hospitalization periods were 7.3 days for the overseas dogs and 7.2 days for the domestic dogs.
Pre- and post-air flight laboratory test results
To search for the risk factors for dogs with MVD on air traveling, an attempt was made to compare the laboratory results before and after the flight. Blood tests, radiography, and echocardiographic data before the flight could only be collected from a small number of dogs. In addition, the most recent data varied from approximately 1 year to a few weeks prior to the flight. Considering the fact that MVD is a progressive disease, data within 4 months prior to MVR were used, since this was the average period for domestic dogs with MVD awaiting MVR after the date of surgery was appointed. The medical records of 10 dogs were used in this study. Values related to heart failure were assessed, including heart size from echocardiography and hematocrit, total protein, blood urea nitrogen, and creatinine levels from blood tests. Enlarged heart size based on the American College of Veterinary Internal Medicine (ACVIM) consensus guideline [7] was recorded in all 10 dogs prior to the flight, but was confirmed in only seven dogs at the time of initial examination after arrival. Dehydration (diagnosed if two of the following three criteria were met: hematocrit > 55.0%, total protein > 7.2 g/dl, or blood urea nitrogen > 29.2 mg/dl in blood test results) was not observed in any of the dog prior to the flight and was confirmed in one dog after arrival. As for prerenal azotemia (defined as blood urea nitrogen > 29.2 mg/dl and creatinine > 1.4 mg/dl from blood tests), two dogs had persistent blood levels concerning azotemia, one resolved at the time of examination, and two developed after arrival. No symptoms observed during the flight correlated with laboratory results. No data prior to flight was available for the assessment of the two dogs that died after arrival.