Gross Pathology of Herons and Egrets at a Wildlife Rehabilitation Center in Northern California - Molly Horgan DVM Candidate, Class of 2020 UC ...
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Gross Pathology of Herons
and Egrets at a Wildlife
Rehabilitation Center in
Northern California
Molly Horgan
DVM Candidate, Class of 2020
UC Davis School of Veterinary Medicine
Study
• Necropsy of all herons/ egrets that died in a 6 week
period in the summer of 2018 (June – August)
• Gross, occasionally diff-quick cytology
• Budget ~ $0
• Objectives:
• Metabolic bone disease
• Why birds die/ don’t do well
• Limitations
• Only gross findings
• Short period of time, vast majority young animals,
one region
TOTAL NECROPSIES
n=145
EUTHANIZED DIED
n=108 n=37
METABOLIC BONE DISEASE CLINICAL DECLINE TRAUMA SEPTIC ARTHRITIS OTHER
n= 39 n= 32 n= 24 n= 9 n= 4
Species and age
Number
SPECIES
Black-Crowned Night Heron (Nycticorax nycticorax) 33
Young snowy egrets, black
Cattle Egret (Bulbulcus ibis) 9
Great Blue Heron (Ardea Herodias) 2
Great Egret (Ardea alba) 7
crowned night herons,
Green Heron (Butoroides virescens)
Snowy Egret (Egretta thula)
LIFE STAGE
21
73
Hatchling
Nestling green herons 5
35
Fledgling 95
Older juvenile 9
Adult 1
Anatomy
TRACHEA
THYROID GLAND
PARATHYROID GLAND
HEART
LIVER
Anatomy
ESOPHAGUS
TRACHEA KIDNEYS
LUNGS
LUNGS
HEART SPLEEN
LIVER
VENTRICULUS
Anatomy
OVARY
TESTES
Female Male
43/145 Birds
43/145 Birds
Definitive bird host
Bird sheds parasite
eggs into the environ-
ment in feces
Birds feed on infected transport hosts.
Infective larvae reach sexual maturity
within bird host Bird feeds on infected fish
Eustrongylides sp.
then larvae develop to
sexual maturity
Transport (paratenic hosts)
First stage larvae develop
in eggs eaten by oligochaetes
(freshwater aquatic worms)
Infected minnows are fed upon
by species other than birds First intermediate host
Minnows and other
small fish feed upon
oligochaetes
Third stage larvae
become encapsulated Eggs hatch within oligochaetes;
within body of fish second-and third-stage larvae are
Second intermediate host produced within oligochaetes
Figure 29.1 Life cycle of Eustrongylides sp.
224 Field Manual of Wildlife Diseases: BirdsSecondary infections • Abscesses • Liver (7) • Lung (5) • Airsacculitis (3) • Renal (1)
Eustrongylides • 43/145 birds • Death – 10 • Anorexia, weight loss, hypothermia à euthanasia – 12 • Incidental/ resolving – 21
Metabolic Bone Disease • Most common reason for euthanasia during study time period
Metabolic Bone Disease NORMAL
METABOLIC BONE DISEASE
• Main components of bone:
• Organic matrix – mostly collagen
• Mineral – hydroxyapatite = calcium and phosphorous
MBD = family of bone disorders resulting from a disturbance
in Ca homeostasis
Many potential causes: diet, toxins, hormonal imbalances, renal failure,
neoplasia…Parathyroid hormone
MAIN FUNCTION
PTH
= PREVENT Activation of
BLOOD CALCIUM Blood Ca vitamin D
FROM GETTING Ca reabsorption
TOO LOW
Ca pulled from bone
blood CaMetabolic Bone Disease
NO MBD MBD
Parathyroid gland diameter
4
3
diameter (mm)
2
1
0
D
D
B
B
M
M
o
N
Yellow arrows = thyroid gland; red arrows = parathyroid glandVitamin D Inactive vitamin D in blood
Ca and P absorption
from GI tract
liver
Ca reabsorption
in kidney
Bone formation
kidneys
Active vitamin DMetabolic Bone Disease • Increase from previous year in both numbers at intake and developing in care • Considered separately
MBD in care - Diet
• Dietary causes of MBD: ↓ Ca, ↓ P,
↓ Ca:P ratio, ↓ Vitamin D
• 2017 – night smelt
• No MBD
$$$$$
• 2018 – capelin
• Supplemented CaCO3 for Ca:P ratio of 2:1
• Lots of MBDCapelin Vitamin D Content
• Capelin – 99IU/100g
• Herring – 1257IU/100g
• MBD in African penguins
fed capelin
• No measurable Vitamin D
in capelinProportion of birds necropsied with MBD
Supplementation
= 3240 IU/kg BW
Oral Vitamin D3
* Only including animals that developed MBD in careVitamin D
Parathyroid
hyperplasia
PTH
Ca and P absorption from
GI tract Blood Ca
Ca reabsorption in Calcium pulled from
kidney bone
Bone formationMBD at intake from April 1st –August 9th
Location 2017 2018
Total 28/637 (4%) 51/446 (11%)
At intake = noted at intake exam or within 3 days of admissionMBD at intake from April 1st –August 9th
Location 2017 2018
Total 28/637 (4%) 51/446 (11%)
Concord 2/15 (13%) 0/20 (0%)
Fairfield 4/86 (5%) 3/39 (8%)
Oakland 2/105 (2%) 4/25 (16%)
Sacramento 5/36 (14%) 2/61 (3%)
Santa Rosa 11/258 (4%) 35/176 (20%)
At intake = noted at intake exam or within 3 days of admissionMBD at intake from April 1st –August 9th
Location 2017 2018
Total 28/637 (4%) 51/446 (11%)
Concord 2/15 (13%) 0/20 (0%)
Fairfield 4/86 (5%) 3/39 (8%)
Oakland 2/105 (2%) 4/25 (16%)
Sacramento 5/36 (14%) 2/61 (3%)
Santa Rosa 11/258 (4%) 35/176 (20%)
At intake = noted at intake exam or within 3 days of admissionhttps://sanfrancisco.cbslocal.com/video/3743071-santa-rosa-hilton-hotel-engulfed-in-flames-from-tubbs-fire/
TOXINS?
Laguna de Santa Rosa
Watershed
iver
ek
Cre
an R
k
Cree
reek
hC
ilo
Sh
ssi
Pool
r
Ru
dso
Cree
Wi n
st k
We
ark
M
La g u n
a
Santa Ros a
Cre
ek
Ma
ntan
de
zas
Cre
ek
ek
re
Sa
nC
ta lga
n
Co
Ro Hinebaug h Cree k
sa Copeland
Cre
ek
Legend
Laguna Watershed
0 1 2 3 4 5 Miles
Streams
Incorporated Cities 0 1 2 3 4 5 Km
https://www.nytimes.com/interactive/2017/10/14/us/california-fire-building-damage.htmlVisceral Gout – 10/37 birds that died
Visceral Gout
J
Protein Uric acid
breakdown Excreted by kidneysVisceral Gout
J
Protein Uric acid
breakdown Excreted by kidneys
Reduced excretion by kidneys
L
? Toxin?Visceral Gout DOSE = 0.5MG/KG SID • 8 on current course, mean tx 12 days, median 4 days, range 2-36. • 2 died weeks after receiving 1 or 2 doses • Significantly associated with administration of meloxicam (p=0.001) • Not majority of animals treated with meloxicam • 57 birds necropsied that received meloxicam • 15 released during study time period
Intestinal perforation
• n = 4 (3 BCNH, 1 GRHE)
• 1 died, 3 euthanized
• Significantly associated with
meloxicam (p = 0.02)
• Mean tx 17 days, range 9-
31 daysPinterest.com
1.6mg/kg PO BID x 15d
“No apparent negative changes in several renal,
gastrointestinal, or hemostatic variables in healthy Hispaniolan
Amazon parrots”.Beautyofbirds.com
0.5mg/kg IM BID x 14d
“does not cause clinically relevant changes in CBC or plasma biochemical
values, renal-associated lesions, or adverse muscle effects”Allaboutbirds.org
1, 10, 20mg/kg PO BID x 7d
“No clinical signs or mortality were observed in any group. No significant
differences of clinical relevance were found in results of the packed cell
volume, total solids, and biochemical panel, and no evidence of renal
toxicity was found in the treatment or control groups.”https://www.hbw.com/ibc/species/indian-vulture-gyps-indicus
Survey-based study of vets and zoos on outcome of NSAID treatment of over
870 birds from 79 species
Diclofenac, carprofen, flunixin à mortality reported
“In contrast, there were no reported mortalities for the NSAID meloxicam,
which was administered to over 700 birds from 60 species.”Meloxicam • Need more studies to say definitively that meloxicam is a cause of renal failure/ intestinal perforation in herons/egrets • Possible reasons for adverse effects in herons/egrets vs other birds • Extended half life • Young age/ illness • Increased sensitivity to COX inhibition
EUSTRONGYLIDES – 10
GOUT - 10
EUSTRONGYLIDES – 12
INTESTINAL PERFORATION - 2Other findings Finding Number of animals affected Metabolic bone disease 47 Eustrongylidiasis 43 Liver abscess(es) 14 Visceral gout 10 Septic arthritis 9 Lung abscess(es) 8 Intestinal perforation 4
Conclusions • Gross necropsy can be useful! • (but there are limitations) • Suspect Eustrongylides in young herons/egrets that die or have persistent weight loss, anorexia, hypothermia, regurgitation • Consider Vitamin D deficiency when faced with MBD, supplement birds on a diet of capelin • Caution may be warranted using meloxicam in herons and egrets
THANK YOU! •Dr. Rebecca Duerr •Staff/ volunteers at IBR •Dr. Brian Murphy •NWRA •Shak Makhijani – photo credit (live birds)
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