The question is: why are you planning to "control" these seabird parasites?

Host and parasites are part of their ecosystem and result from long time co-evolution. In the wild, (I guess your seabird colonies are not in zoo), parasites are one among many drivers of host evolution and they participate in the host population regulation, along with predators, food availability and natural hazards. Reciprocally, hosts participate in the regulation of parasite population.

That is quite different from what one could observe in a chicken coop, a very artificial ecosystem without most of the natural regulation loops.

Are you sure, the use of any "acaricide" would not result in unexpected results, potentially worse than the first tick problem. Think about the consequences on global environment of using DDT and other organochlorine or organophosphate pesticides to control mosquitoes and malaria since the 1940's – mosquitoes and malaria are doing well, and we find DDT in whale and polar bear fat…

If you succeed in controlling ticks, the seabird population may grow until exhaustion of fish populations on which it feed. Therefore, starvation (or other disease) will replace ticks in seabird population control…

From an ethical point of view, this is very questionable, even if you plan to use "natural" or "sustainable" methods.

Could you clarify which ticks? I'm not a seabird person but I would guess you are talking about argasid ticks, and because some of these like Ornithodoros are important livestock disease vectors or pests there is a fair bit of literature on their control - some of which might be relevant.

Unfortunately the potential for using chemical or biological control effectively in field environments like seabird colonies isn't clear.

Without information about the ticks you're asking about it's difficult to know if this is relevant, but we wrote about chemical and biological control of Ornithodoros in the attached review. The most relevant section is pasted below. We were mainly looking at O. erraticus but the same methods would be as effective for many other soft ticks.

Various chemicals have been proposed for [chemical control of Ornithodoros], including methyl or methylene bromide fumigation followed by the application of carbaryl (Endris and Hess 1992), the treatment of hosts with ivermectin or chlorpyrifos (Soll et al. 1984), or the direct application of hexachlorocyclohexane (HCH) or dichlorodiphenyltrichloroethane (DDT) (Gil Collado 1955). However, in each of these cases, effectiveness under field conditions remains unknown (Astigarraga et al. 1995, Manzano-Román et al. 2006). Additionally, the use of most of these chemicals is restricted in the EU, particularly for food animals. The exception is ivermectin and further research into its effectiveness is required, although its short period of activity relative to the interval between blood meals of adult O. erraticus means that repeated treatments would be necessary and the potential for development of resistance would need to be investigated.

More recently, biological control has been suggested. Significant levels of mortality have been observed in the laboratory following treatment with Beauveria bassiana, Lecanicillium lecanii, and Tolypocladium cylindrosporum, of which the most effective (B. bassiana strain Bb2157 and T. cylindrosporum strain T1) achieved mortalities of 62% and >70% 28 days after application (Zabalgogeazcoa et al. 2008, Herrero et al. 2011). However, further work is needed to investigate effectiveness under field conditions (Willadsen 2008).

Article The Medical and Veterinary Role of Ornithodoros erraticus Co...

Thank you so much for your input! I am talking about Soft ticks (Argasidae) and I have only found Ornithodoros so far. I will read the articles you have sent and share my comments. We will test control methods during 2017 so I can share if things work. Kindest regards!

The question is: why are you planning to "control" these seabird parasites?

Host and parasites are part of their ecosystem and result from long time co-evolution. In the wild, (I guess your seabird colonies are not in zoo), parasites are one among many drivers of host evolution and they participate in the host population regulation, along with predators, food availability and natural hazards. Reciprocally, hosts participate in the regulation of parasite population.

That is quite different from what one could observe in a chicken coop, a very artificial ecosystem without most of the natural regulation loops.

Are you sure, the use of any "acaricide" would not result in unexpected results, potentially worse than the first tick problem. Think about the consequences on global environment of using DDT and other organochlorine or organophosphate pesticides to control mosquitoes and malaria since the 1940's – mosquitoes and malaria are doing well, and we find DDT in whale and polar bear fat…

If you succeed in controlling ticks, the seabird population may grow until exhaustion of fish populations on which it feed. Therefore, starvation (or other disease) will replace ticks in seabird population control…

From an ethical point of view, this is very questionable, even if you plan to use "natural" or "sustainable" methods.

A very good comment by Maurice Mahieu. Really, why is it so necessary to control ectoparasites of seabirds? Or, perhaps, you plan to estimate how different parasite burden influences bird populations?

Best wishes, Igor

Dear All,

I definitely agree with you in that we should not alter the natural balance between animals and their parasites. However, this is a special case. It is a colony that was human-established because of the scarce number of colonies (due to human invasion). The seabird species is endangered and every year they have massive infestation of parasites. Many abandoned chicks at the nest or roaming around the colony together with massive deaths. The ones that survive have to be sent to a rehabilitation centre and this place collapse with these many sick chicks. It is not clear what is driving the parasites to thrive because the colony has TOO MANY stress factors. However, they want to treat the colony/birds. That is why we want to suggest a less invasive method where they can maybe treat an area and see if it works, while we are figuring out what is the main problem in the colony. The colony managers just do not want to have the massive deaths/exodus of chicks at the end of the every year. This is why I am asking for some advice.

We will only try some method during the year, and after gathering enough information. Even maybe after an expert meeting about the topic. We really need to do something now.

Thank you very much for your advice and support! Marcela

Maurice: it is certainly true that chemical control can have substantial and long-lasting off-target effects. However, we can't infer from the information in the question that the existing parasite burden is at 'natural' levels - in many communities recent environmental change has already resulted in hosts experiencing a higher parasite burden than seen historically, for example via higher stresses experienced by the bird population. And the ethical case is actually stronger than you imply given that ectoparasites, particularly at high loads, have a substantial welfare impact. Lastly (although it's straying off-topic) it's worth recognising that malaria isn't "doing well" - it's in a period of pretty rapid decline, and the use of DDT was, and is, highly effective at controlling the target species. It can certainly also have catastrophic side effects, particularly  if used inappropriately. Chemical control still forms an essential part of vector management in many areas today, but whether it is a suitable option for a given situation always depends on other factors.

I would agree that in the situation described chemical control is likely to be difficult to achieve without off-target effects, but if control is essential for some reason then I'm struggling to think of anything that would be more likely to actually achieve the desired result.

(Lastly - "why are you planning to control these seabird parasites" is *a* question, but it literally isn't *the* question - the actual question is up there at the top!)