Clinical parameters of hypervirulent Klebsiella pneumoniae disease and ivermectin treatment in New Zealand sea lion (Phocarctos hookeri) pups

Abstract

Hypervirulent Klebsiella pneumoniae infection causes significant mortality of endangered New Zealand sea lion pups at Enderby Island, Auckland Islands. Gross necropsy and histopathology findings are well reported, but little is known about the clinical course of disease in affected pups. To determine factors feasible as clinical screening tools for hypervirulent K. pneumoniae in live pups, 150 pups over two field seasons (2016–18) were recruited shortly after birth for a prospective cohort study. A randomised controlled clinical treatment trial with the anthelmintic ivermectin was conducted concurrently and risk factor data and biological samples were collected approximately fortnightly. Treatment with ivermectin has been demonstrated to reduce the risk of hypervirulent K. pneumoniae mortality in pups, so effects on clinical parameters between the treated and control cohorts were also investigated. A broader sample of pups were monitored for clinical signs to investigate the course of disease in affected pups. Clinical signs, haematology and oral and rectal swabs to detect gastrointestinal carriage of hypervirulent K. pneumoniae were not useful for detection of disease prior to death. Of those pups that died due to hypervirulent K. pneumoniae, only 26.1% (18/69) had any clinical signs prior, likely a reflection of the peracute course of disease. On comparison of haematological parameters between ivermectin-treated and control pups, significantly lower total plasma protein and higher eosinophil counts were seen in control versus treated pups, however standard length as a surrogate for age was a more important influence on parameters overall than ivermectin treatment. This study also highlighted a cohort of pups with severe clinical signs suggestive of hypervirulent K. pneumoniae infection were lost to follow up at the end of the monitored season, which could be contributing to cryptic juvenile mortality.

Mitigating disease risk in an endangered pinniped: early hookworm elimination optimizes the growth and health of Australian sea lion pups

“…Decreasing counts attributable to ontogeny were typically characterized by a decrease in each of the individual WBCs -apart from the marked increase in eosinophil count attributed to the onset, and persisting for the duration of, patent hookworm infection. The close temporal relationship between patent hookworm infection and systemic eosinophilic inflammation, is previously reported in treatment trials in otariid species (21,24,50). Treatment-related changes in the remaining WBCs were less significant, excepting the frequently higher lymphocyte counts in the untreated pups, also reported in those earlier studies.…”

“…Results of this study, particularly for TPP concentration, highlight the importance of including age and other contributing factors in modelling of disease or treatment impact on pup hematological parameters -an outcome also evident in a recent disease investigation in the New Zealand sea lion (50). The declining TPP concentration in the recruitment-to-first recapture period in untreated pups of the youngest <14 d cohort contrasts with a mild increase in treated pups of that cohort, and more rapid increases in treated and untreated pups of the older two age cohorts.…”

“…Lower TPP levels have previously been reported in Australian sea lion pups with patent, versus pre-or postpatent hookworm infection, and reasonably attributed to intestinal hemorrhage (in association with lower RBC counts) caused by the blood-sucking nature of the intestinal parasite ( 22 ). Lower TPP has also been reported with hookworm-infected (versus treated) New Zealand sea lion pups, albeit with an important age-related influence ( 50 ). In contrast, the two previous treatment trials in the Australian sea lion showed either significantly higher TPP concentrations in the untreated pups at 15–24 d (but not at 36–41 d) post-treatment ( 21 ), or a non-significant trend for the same outcome at 27–67 d post-treatment ( 24 ).…”

Hypervirulent Klebsiella pneumoniae: Characteristic and clinical perspective

“…There are several clinical symptoms caused by hvKP infection in puppy as test animals, such neurological disorders, like decreased consciousness to death, swelling of the joints and even decreased body motoric, several other signs, namely septic arthritis or cellulitis [41]. There are also other symptoms in the ocular such as formation of hypopyon and blepharospasm, rise of the body temperature with the highest temperature 40 o C. There are also some non-specific symptoms such as polyarthritis, pyothorax, suppurative meningitis and subdural hemorrhage [41].…”