Osteoarthritis in two marine mammals and 22 land mammals: learning from skeletal remains

Abstract

The occurrence of osteoarthritis (OA) in marine mammals is still questionable. Here we investigated the prevalence of OA in marine (dolphin and dugong) and terrestrial mammals (Asian elephant, Asiatic buffalo, camel, cat, cattle, deer, dog, domestic goat, horse, human, hyena, impala, lion, Malayan tapir, Assam macaque, mule, pig, rabbit, red kangaroo, sheep, tiger and waterbuck). Skeletal remains obtained from five institutes were used as subjects; a total of 45 different parts (locations) of bones were observed for OA lesions. The prevalence of OA was reported as number of OA lesions/total number of bones. Our results revealed that the presence of OA in marine species (dolphin and dugong) was 2.44% and 3.33%, respectively. In dolphins, the highest OA occurrence was on the left and right humeral trochlea, with 13.68% and 12.63%, respectively, while the highest number of OA lesions in dugongs was on the lumbar vertebrae (8.79%). No significant difference (P > 0.05) in the prevalence of OA between sexes in dolphins and dugongs was observed, but we found a significant difference (P < 0.05) in 24 bone locations of human bones, which had the highest OA prevalence (48.93%), followed by dogs (3.94%). In conclusion, OA can occur in marine mammals, similar to terrestrial mammals, even though their natural habitat is the ocean.

Keywords: bone; degenerative joint disease; land mammal; marine mammal.

Figure 1

Based on cytochrome b (CYTB), a phylogenetic tree was constructed using a neighbor‐joining model to illustrate the genetic relationship and osteoarthritis (OA) occurrence among species, including dog, cat, pig, buffalo, camel, cow, waterbuck, deer, goat, sheep, horse, hyena, impala, kangaroo, lion, tiger, rabbit, tapir, elephant, monkey, human, dugong and dolphin. Numbers are bootstrap values (in percent 1000 replications) of neighbor joining. + = OA occurrence; − = no OA lesions; and ? = species not determined for OA lesions. Green indicates the herbivore groups, and red indicates carnivores and omnivores.

Figure 2

Representative photos of the normal articular surface of canine acetabulum (A), osteophyte formation as a reference for osteoarthritis (OA) (B), and severe osteophyte formation with subchondral bone degradation as a reference for OA (C).

Figure 3

Representative photos of abnormal structures (arrows) such as pathological lesions from fracture (A), and bone degradation from the environment (B).

Figure 4

Osteoarthritis (OA) lesions (arrows) were found in dolphin bones at different locations, such as occipital condyle (A), glenoid cavity of scapula (B), head of humerus and carpal joint (C), and body of vertebrae (D and E).

Figure 5

Osteoarthritis (OA) lesions (arrows) were found in dugong bones at different locations, such as the occipital condyle (A), body of vertebrae (B–D), glenoid cavity of scapula (E), head of humerus (F) and styloid process of ulna/radius (G).

Figure 6

Representative photos showing osteoarthritis (OA) lesions (arrows) in carpal joint of Malayan tapir (A), acetabulum of tiger (B), elbow joint of sheep (C), articular surface of distal phalanx of horse (D), tibial condyle of cat (E), femoral head of monkey (F), femoral head of dog (G), trochlear notch of hyena (H), articular surface of tarsal bone of cattle (I), lumbar vertebra of human (J), and phalanx of Asian elephant (K).