# Presentation: 024836

## WNV Vertebrate Ecology and Biology-Birds

**Nicholas Komar, ScD ****Arbovirus Diseases Branch, DVBID, CDC**** Fort Collins, CO**

## Experimental infection of WNV in 25 species of birds

**Komar et al., 2003, EID 9(3): 311-323; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm**

**Other studies:****Senne et al. 2000****Swayne et al. 2000 ****Langevin et al. 2001****Swayne et al. 2001****McLean et al. 2002**

## Very Competent Species

**	****	****	****  ****	****	****       ****Mean****	****  Reservoir****	****	****	****        Days         Peak****	****Competence**_**Species (n)**__**	**__**    Infectious*  Viremia    Index, c**__***i***_
**Blue Jay (4)****	****	****  4.0****	****	****11.0****	****	****2.6 ****	****Common Grackle (6)****	****  3.0****	****	****9.4****	****	****2.0****	****   ****House Finch (2)****	****  5.5****	****	****8.5****	****	****1.8****	****   ****American Crow (8)****	****  3.2****	****	****10.1****	****	****1.6****House Sparrow (6)  ****	****  3.0****	****	****8.9****	****	****1.6**
***Infectious viremia = log 5 or greater per ml serum****       **

## Moderately Competent Species

**Ring-billed Gull (2)****	****  ****	****4.5****	****	****7.4****	****	****1.3****Black-billed Magpie (3)  ****	****3.0****	****	****8.7****	****	****1.1****American Robin (2)****	****   ****	****3.0****	****	****8.5****	****	****1.1****Red-winged Blackbird (3)****	****3.0****	****	****8.1****	****	****1.0****Killdeer (2)****	****	****  ****	****3.0****	****   ****	****8.1****	****	****0.9****Great Horned Owl (1)****	****4.0****	****   ****	****7.6****	****	****0.9****American Kestrel (2)****	****	****3.0****	****   ****	****8.4****	****	****0.9****Fish Crow (8)****	****	****	****2.8****	****   ****	****6.8****	****	****0.7***** Infectious viremia = log 5 or greater per ml serum**

**Moderately Competent Species**

## Weakly competent species

**Weakly competent species**

## Non-competent species

**Non-competent species**

## Summary of Competence Studies

**Passerines are most competent**
** ****jays, crows, sparrows, finches, blackbirds, etc.**
**Not all passerines are equally competent**
**Not all birds are competent**
** ****pigeons, chickens incompetent**
**Competence does NOT imply Reservoir Status**

## Reservoir Host Criteria

**Competent**
**Naturally Exposed**
**Abundant**

## Natural Exposure: Seroprevalence Studies

**High seroprevalence (typically >30%) in resident birds after epizootic transmission**
**Low seroprevalence (typically <1%) in enzootic foci, in non-resident birds, early in transmission season**

##       Species	       	POS/Total    % POS       
Domestic Goose	     6/    7 		86
Turkey		  	     2/    3		67
Chicken			   89/141		63
House Sparrow	   12/  20		60
Pigeon			   13/  49		27
Canada Goose	     2/    7		29
Mallard		 	     1/  16		  6
Ref: Komar et al. 2001. Emerg. Inf. Dis. 7(4): 621-625.

_**      **__**Species**__**	**__**       **__**	**__**POS/Total    % POS    **_**  **_** **_
**Domestic Goose****	****     6/    7 ****	****	****86**
**Turkey****	****	****  ****	****     2/    3****	****	****67**
**Chicken****	****	****	****   89/141****	****	****63**
**House Sparrow****	****   12/  20****	****	****60**
**Pigeon****	****	****	****   13/  49****	****	****27**
**Canada Goose****	****     2/    7****	****	****29**
**Mallard****	****	**** ****	****     1/  16****	****	****  6**
***Ref: Komar et al. 2001. Emerg. Inf. Dis. 7(4): 621-625.***

## Relative Abundance of Birds, Queens

**	****	****	****	****	****	****	****Relative****	****	****	****	****   Relative****	****  Infection****	****no. of****    Species****	****	**** Abundance****	****     Rate****	****Infections**
**House Sparrow****	****    6000****	****     0.60****	****4186**
**Pigeon****	****	****    1000****	****     0.27****	****  314**
**Mallard****	****	****        60****	****     0.06****	****      4**
**Canada Goose****	****        60****	****     0.29****	****    20**
**Chicken****	****	****          3****	****     0.63****	****      2**
**Domestic Goose****	****          1****	****     0.86****	****      1**
***Ref: Komar et al. 2001. Emerg. Inf. Dis. 7(4): 621-625.***

## Reservoir Potential of Birds, Queens

**	****	****	****       ****A****	****       x****	****     B ****	****     =         C **
**	****	****	****Relative no. ****	****Competence****	****Reservoir****    Species****	****	**** infections****	****   Index****	****Inoculation Index**
**House Sparrow****	****    4186****	****    1.6****	****	****11,000**
**Pigeon****	****	****      314****	****    0****	****	****         0****	**
**Mallard****	****	****          4****	****    0.5****	****	****         3**
**Canada Goose****	****        20****	****    0.03****	****	****         1**
**Chicken****	****	****          2****	****    0****	****	****         0**
***Read: “For every one WNV-infectious ***_***Culex pipiens***_*** infected by a Canada goose, there were 3 infected by mallards and more than 11000 infected by house sparrows”***

## Birds affected by WNV – 162 spp. 

## Avian Mortality:Disease Impact Studies

**Surveillance data lack attack rates, mortality rates**
**Preliminary observations were made in 2002 of three marked crow populations:****Stillwater, OK; Ithaca NY; Chicago, IL**

## Experimental WNV Mortality -1

**American Crow****	****	****20****	****	****100****	****	****8****	****Black-billed Magpie****	****  5****	****	****100****	****	****1****Blue Jay****	****	****	****  6****	****	****  83****	****	****0****House Finch****	****	****	****  3****	****	****  67****	****	****3****Fish Crow****	****	****	****11****	****	****  64****	****	****5****Ring-billed Gull****	****	****  2****	****	****  50****	****	****1****Common Grackle****	****	****10****	****	****  40****	****	****2****House Sparrow****	****  ****	****12****	****	****  25****	****	****5 **
**These birds infected by natural means (mosquito, oral, bird-bird)**

**Experimental WNV Mortality -1**

**Komar et al., 2003, EID 9(3): 311-322; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm**

## Experimental WNV Mortality -2

_**Species**__**	**__**	**__**  **__**	**__** n**__**	**__**mortality rate     controls        **_
**European Starling****	****  ****	****  6****	****	****    0****	****	****2****	****Rock Dove****	****	****	****  6****	****	****    0****	****	****6****Chicken****	****	****	****18****	****	****    0****	****	****24****Ring-necked Pheasant****	****  3****	****	****    0****	****	****0****Canada Goose****	****	****  3****	****	****    0****	****	****0****American Robin****	****	****  3****	****	****    0****	****	****3****Red-winged Blackbird****	****  3****	****	****    0****	****	****0 ****Mourning Dove****	****	****  3****	****	****    0****	****	****3****Budgerigar****	****	****	****  3****	****	****    0****	****	****3****Monk Parakeet****	****	****  3****	****	****    0****	****	****3****Japanese Quail****	****	****  3****	****	****    0****	****	****3****Northern Bobwhite****	****	****  3****	****	****    0****	****	****3**

**Komar et al., 2003, EID 9(3): 311-322; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm**

## Alternative Transmission in Birds

## WNV Cage Mate Transmission 

_**Species**__**	**__**	**__**  No. of cages**__**	**__**No. of transmissions        **_
**American Crow****	****	****  4****	****	****	****4****Black-billed Magpie****	****  3****	****	****	****2****Blue Jay****	****	****	****  2****	****	****	****2****Ring-billed Gull****	****	****  1****	****	****	****1 ****Chicken****	****	****	****18****	****	****	****1 ****Other species (n=13)****	****30****	****	****	****0**

**Komar et al., 2003, EID 9(3): 311-322; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm**

## WNV Oral Transmission 

_**Species**__**	**__**	**__**  **__**	**__**n**__**	**__**dose**__**	**__**	**__**no. viremic        **_
**Common Grackle****	****	****4****	****1000 pfu****	****	****4**
**House Finch****	****	****	****1****	****mosquito****	****	****1**
**House  Sparrow****	****	****6****	****10****7**** pfu****	****	****6**
**American Crow****	****	****6****	****sparrow****	****	****5**
**American Crow****	****	****3****	****10****7**** pfu****	****	****3**
**Great Horned Owl****	****	****1****	****mice****	****	****	****1****	****	****	**

**Komar et al., 2003, EID 9(3): 311-322; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm**

## Cloacal shedding in crows

**Cloacal shedding in crows**

**Threshold of infectiousness ?????**

## Persistence of WNV in Tissues

**	****	****	****	****	****  ****Viral****	****     ****	****	****Days**_**Species**__**	**__**	**__**  Tissue**__**	**__**  Load**__**	**__**	**__**     post-viremia**_**Killdeer 1****	****	****  Skin****	****	****  110 pfu/0.5 cm****3****	****  9****Killdeer 2****	****	****  Spleen****	****  550****	****	****	****10****Killdeer 2****	****	****  Skin****	****	****  20,000****	****	****10****Mourning Dove****	****  Kidney****	****  100****	****	****	****11****Budgerigar****	****	****  Heart****	****  130****	****	****	****13****Blue Jay****	****	****  Eye****	****	****  360****	****	****	****  9****Common Grackle****	****  Skin****	****	****  380****	****	****	****11****Common Grackle****	****  Eye****	****	****  150****	****	****	****11****House Sparrow 1****	****  Skin****	****	****  370****	****	****	****  8****House Sparrow 2****	****  Spleen****	****  120****	****	****	****10****House Sparrow 2****	****  Lung****	****	****  590****	****	****	****10****House Sparrow 3****	****  Brain****	****  300****	****	****	****  8  **

**Komar et al., 2003, EID 9(3): 311-322; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm**

## Birds as Dispersal Vehicles

**No hard evidence yet**
**Laboratory studies pending**
**Field studies unsuccessful to date**
**Significance of prolonged viral persistence in organs?**

## Ecological Factors Affecting Transmission

## Pigeons seroconverted 270% more frequently in the canopy in New York City:32 vs 12 in 2002

## Acknowledgments

## West Nile Virus:  Primary Passerine-Culex Transmission Cycle

**West Nile Virus:  Primary *****Passerine-Culex***** Transmission Cycle**