it is a rather long list of mechanical vectors of diseases. A hurried and very incomplete one is the following: biting flies (Tabanous spp. Stomoxys spp., Pangonia spp.) vector of Trypanosoma evansi (camels) , non-biting blow flies (Chrisoma albiceps, C. marginalis, Musca domestica etc ) and scavengers such as hyena (Crocuta crocuta) and vultures (e.g. Gyps africanus) vector of Anthrax, anything passing through an infected FMD area vector of FMD! Soil various Clostridium spp, anthrax, Sarcoptes scabiei etc, any objects of areas where blue wildebeest (Connochaetes taurinus) have given birth vector of MCF , fences, poles and common objects used in daily husbandry practices Sarcoptes scabiei, Dermathopilus congolensis, contaminated (by rabid saliva) Acacia or other spiny shrub vector of rabies in kudu (Tragelaphus strepsiceros) orf , various species of Muscidae keratocongiuntivitis and other common bacterial infections, various species of culicoides LSD and lots of viruses, water lots of gastrointestinal parasites and many bacterias!, Ornithodorus spp vector of ASF. Perhaps the best mechanical vector are un-sterilized vaccination needles.

For object vectors (fomites), bird feeders have been implicated in several emerging songbird pathogens, including Mycoplasma gallisepticum and Trichomonas gallinae. Although bird feeders are likely serving both as fomites and as attractive food sources that encourage dense aggregation (and thus elevated contact and/or shedding). 

Fischer et al 1997, Emerging Infectious Diseases

Dhondt et al 2007, Avian Pathology

Lawson et al 2012, Proceedings B

Also see Robb et al 2008 Frontiers in Ecology

There's also similar patterns emerging for the spread of bacterial pathogens of ungulates amplified by feeding stations (especially Palmer & Whipple 2006).

Well Bruce,  It has to be the insect.  There are so many transmittable pearasites, diseases and disease agents spread by them.  In the group of the insect I would suspect that mosquitoes economically may be the most important, but you know that.  I do have concerns about raw bivalve consumption by humans, this is most usually oysters but as you know other raw suspension feeding mollusca are eaten.  There is possible a potential problem with cholera as the strains 001 and 139n have been found associated with ballast water of ships.  So insects I believe but we should not forget the rest.  WE have more of a responsibility for the molluscan end as this is where our research has brought us.

Bruce, flies mechanically transmit Vibrio cholerae.  Among the seemingly competent mechanical vectors are Drosophila and Musca species.  Off hand, I don't know if this meets the strictest definition of mechanical transmission since at least in the Drosophila model the bacteria proliferate in the "vector".  It also seems plausible that for pathogens that produce toxin (e.g.. other enterics) flies could serve as mechanical vectors moving toxin to food that is consumed by hosts without actually transmitting or supporting viable bacteria.  

I venture to say that it might simpler to catalog possible "vectors" by taking a look at the parasites and how they interact with their common vectors. For example Trypanosoma cruzi the agent of Chagas disease doesn't actually "enter" its common vector, one of several assassin bug species, instead it exits the gut in the bug's excreta as the bug is feeding on a mammal, such as a human, and enters the body through sensitive mucosa or any open wound. Not surprisingly people have become infected by eating food contaminated with the feces of an infected bug (there is a classic example of someone in Brasil becoming infected with Chagas after drinking a fruit smoothy). More close to my home, Eastern equine encephalitis virus (EEV) is transmitted mechanically by mosquitoes. In this case viruses remain in the proboscis of the mosquito after it bites an infected host and are introduced into the next host upon a second feeding. This strategy does not require much adaptation to the vector and so alternative forms of transmission no doubt occur. However, there a million questions still to be answered about that disease. Robust and virulent parasites (EEEV has a ~60% mortality upon infection in humans) that exploit mechanical transmission are really hard to work with.

The members of the families Fanniidae, Muscidae and Blattaria are common mechanical vectors implicated in Veterinary, Medical and agricultural entomology. Check the Books: Entomology for Medical Students by Mike Service, 4th Ed 2008 or 5th Ed 2012 and, Medical and Veterinary Entomology By Mullen and Durden, 2nd Ed 2009 to get the details

Simply the mass movement of cattle from country to country is an important potential vector or disease transmission.  There are massive exports of beef from countries such as Mexico, Argentina and Uruguay, and their source (specific ranches and holding areas) are rarely documented. This makes tracing the origin of disease or contamination for disease control purposes almost impossible.  The World Health Organization and the World Trade Organization both have potential jurisdiction over this. 

Thanks for all the thoughtful responses/answers, which are very helpful to me.  I have attached here one of our papers on mechanical transmission by insect in a complex ecosystem where livestock, wildlife, and people occur in close proximity and interaction.

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