Longevity of the mites Dermanyssus gallinae and Liponyssus sylviarum

EXPERIMENTAL

PARASITOLOGY

Longevity

14, 358-366 (1963)

of

the Mites Liponyssus A.

Ministry

of Agriculture,

Dermanyssus sylviarum

gallinae

Kirkwood

Fisheries and Food, Central Veterinary Weybridge, Surrey, England

(Submitted

and

for publication,

24 January

Laboratory,

1963)

Dermanyssus gallinae lived for as long as 34 weeks without a blood meal, but Liponyssus sylviarum lived for only 3 weeks. A special perch which was designed for these experiments provided a ready means of trapping large numbers of mites. It also proved an efficient trap when only small numbers of mites were present. Liponyssus was observed on chickens throughout the year, and while some birds maintained a high level of infestation, others carried only a few mites.

gallinae The “Red Mite” Dermanyssus (Degeer, 1778) and the “Northern Fowl (Canestrini and Mite” Liponyssus qdviarum Fanzago, 1877), are two of the most serious ectoparasites of poultry. Dermanyssus feeds mainly at night and normally stays on the birds for only 1-2 hours to feed, returning to hide in the cracks and crevices of the poultry house before daylight appears. The mites may therefore remain unnoticed by the poultry farmer, particularly during the winter months when they are present in small numbers only; the population, however, rapidly increases in the summer (Harrison, 1960). Liponyssus does not hide and its entire life cycle can take place on the birds. Control measures against these two mites include treating the birds with an acaricide and moving them into fresh quarters. The infected birdhouse has to be thoroughly cleaned out and also sprayed with an acaritide. Even these precautions may fail to kill all the mites, particularly Dermanyssus, which may hide in deep crevices of the shed. It has been suggested that an infestation can be eliminated from a building by removing the birds and thus subjecting the mites to starva-

tion. It is therefore important to know how long the mites can survive without feeding. Although it is generally accepted that Dermanyssus can survive for long periods without a blood meal there are little precise data available. It was therefore decided to study the survival of Dermanyssus and Liponyssus kept both in the laboratory and in the natural conditions of a chicken hut. In addition the opportunity was taken of following the progress of an infestation of Liponyssus on birds. MATERIALS

Experimental

AND

Infestations

METHODS

in a Chicken

Hut

In the summer of 1961 two huts were erected in a bird-proof compound and raised over water to prevent escape of mites. Each hut, which had a window on one side only, measured 10 X 7 feet. Poultry litter containing Dermanyssus and Liponyssus was collected from a number of field infestations and stored in glass jars at normal outdoor temperatures until June 21, when it was scattered on the floor of hut 1. Fifteen White Leghorn cockerels were then put into the hut, which was examined every week. By the middle of August (8 weeks) many Dermanys-

POULTRY

MITE

sus were seen, especially on the underside of one of the perches. Their numbers steadily increased over the next few weeks so that by the middle of September there were many thousands of red mites in all parts of the shed, in cracks and crevices, in folded pieces of cardboard laid on the floor to provide a hiding place, and particularly in large groups on the underside of the perch near the window. By contrast, a perch further away from the window was rarely used by the birds and had few mites on it. No Liponyssus could be found in the shed itself but there were several on the birds, some of which were more heavily infested than others. Trapping the Mites Dermanyssus Since the red mites were hiding in every part of the shed, some method of encouraging them to remain in one area where they could be easily observed was needed. Harrison (1960) was able to trap mites by using a chicken which was available to the mites for a set period during the night, but in the present experiment a live bait could not be

359

LONGEVITY

used as no blood feeds were to be allowed. Red mites prefer to hide in cracks of the perch or in nesting boxes. Wood ( 1917) suggested that they,otherwise have difficulty in finding a host, and that they will not leave the perch until the infestation has become very heavy, presumably when no more room is left for them in which to hide. In the present experiment it was noticed that most of the mites remained on the perch nearest to the window, where the birds themselves preferred to sit, and so with this in mind a special perch was designed to provide a suitable hiding place for large numbers of mites. This perch was made of three lo-foot lengths of 1% x g soft wood (A, B and C) which, when fitted together, formed a perch 10 feet x 1% inches x 2% inches (Fig. 1). A groove s inch deep by s inch wide was made along the top and bottom of the middle length B, which was cut into Z-foot sections. These were placed together in line between the other two lengths A and C. The three lengths were then held together with g inch bolts fitted at the mid point of each of the

SIDE VIEW

TOP VIEW AcrC[

e

.

.

FIG. 1. The red mite perch in section.

0

.

)

360

KIRKWOOD

Z-foot sections which could then be swung open (Fig. 2). Holes 3/1e inch in diameter were drilled 18 inches from the end and at l-foot intervals through A and C but not passing through B. Similar holes were drilled through B but offset 3 inches from those in A and C. It was hoped that the grooves (which the mites could find by way of the holes in both the top and under side of the perch), would provide a natural place in which most of the mites would choose to hide. At the same time it would be possible to examine them when necessary. On October 4 the old solid perches were taken out of the shed and the new perch fitted opposite the window. It proved very effective and many fed mites were seen in the grooves after only one week. Counting the Mites Liponyssus The birds were examined for Liponyssus every 2 weeks and the degree of infestation recorded. It is very difficult in experiments of

FIG. 2.

this kind to devise an accurate an easy technique for making regular counts of the number of active parasites on a live host. If all the examinations are made by the same operator, however, the degree of accuracy is such that comparisons can be made (Edgar et al., 1949). The infestation usually has to be expressed in relative terms. This may be done by using a coding system such as “H” for a heavy infestation and “L” for a light infestation, or in terms of numbers based on a standard which may itself be an arbitrary figure. We favored a method in which the mites were actually counted. A general description did not seem desirable as only obvious changes in the degree of infestation would be noticed. Harshbarger and Raffensperger (1961) evaluated various methods of estimating infestations and found that the most accurate were those based on the number of parasites that could be counted in 1 minute.

The perch can he opened to expose the mites in the grooves.

POULTRY

MITE LONGEVITY

For the present experiments it was decided to examine the vent area only as this is where nearly all of the mites are to be found. Mites were counted for up to 1 minute, but if there were more than 60 mites the number was estimated instead. The birds were so examined every 2 weeks and always by the same person. It is apparent from Table I that this method gave reasonably consistent results; the number of mites did not vary greatly from month to month. Studies in the Laboratory Dermanyssus (nymphs and adults) were picked from the grooved perch by means of a fine brush and placed individually in 1 X g inch glass tubes, Each tube was lightly plugged with cotton wool and contained a strip of filter paper. The tubes were divided into three lots and stored in the dark in a cold cabinet (constant at lO”C), room temperature (approx. 20”(Z), or in a chicken hut (see Table II for the temperature data). Dermanyssus requires a moderate amount of moisture for survival (Wood, 1917). The chicken hut and the cold cabinet were found to have quite high humidities and in these two places the tubes of mites were packed in cardboard boxes. The tubes stored at room temperatures, where the humidity was comparatively low, were kept over damp cotton wool in sealed glass jars in the dark. Feathers infested with large numbers of Liponyssus were also stored in tubes at the three temperatures used with Dermanyssus. Liponyssus requires a fairly high humidity (Chamberlain and Sikes, 1950), and so all the tubes were kept over pads of damp cotton wool in large sealed jars in the dark. OBSERVATIONS

AND RESULTS

Dermanyssus A week after being placed in position (October 11) the grooved perch was found to be full of mites (Fig. 3), but no mites could be found elsewhere in the hut. When the weather

361

became cold with the temperature at night as low as -3.0°C, the mites became inactive and ceased to take blood feeds from the chickens. They were no longer likely to increase in numbers, and so on November 30 the birds were transferred to hut 2. Observations could now be commenced on the survival of Dermanyssus under natural conditions but without a blood meal in hut 1 while the observations on the infestation of Liponyssus on the birds could be continued in hut 2. Many hundreds of red mites were still alive in the perch at the end of April, having thus survived the winter with temperatures ranging from -10” to 27°C as shown in Table II. They were, however, becoming quite active, and when the perch was knocked the mites would swarm out in large numbers. Many were still alive at the end of May but the population rapidly decreased in June. Most of them must have begun to search for a blood meal, as only a few dead mites were to be found in the perch itself. On June 27, only 56 live mites remained, and by July 18, only six. The following week there were none, and although a very careful search was made, no mites could be found elsewhere in the hut. Some Dermanyssus had thus survived for 33 weeks without a blood meal. It was noted that Dermanyssus mites were rapidly attracted to the perch and it seemed that its use might facilitate the detection of a red mite infestation which might not be otherwise noticed. To observe the sensitivity of this method 30 red mites which had been kept in glass tubes for 6 weeks were put on a chicken in a hut fitted with such a perch. The following day 12 engorged mites were found inside the perch. In another experiment, an open box containing litter infested with red mites was put on the floor of a shed containing chickens, and the next day there were many fed mites in the grooves of the perch. The Dermanyssus in glass tubes were examined every 2 weeks. They survived for as long as 34 weeks (see Table III), and it is

Sept. 8n 8 27 30 43 33 24 30 0 14 0 0 50 100 50

Oct. 16 6 46 6 400 65 30 30 0 36 0 0 200 200 300

Der. 100 75 500 75 20,000 2000 500 150 1000 150 7s 75 2000 5000 1000

KOV.

100 25 100 100 10,000 200 500 1000 200 400 300 60 2000 10,000 1000 200 32 500 75 3000 50 50 50 100 SO 250 15 1000 5000 2000

Jan.

-

-

-,“--

-__---

only.

56 25 100 100 5000 50 100 25 2s 500 200 100 2000 10,000 500

Feb.

* The ti~ures refer to the estimated numbers of mites on the vent area

Number of Bird 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

The Progress of an Infestation

-

75 25 300 55 5000 50 50 50 100 15 500 200 5000 10,000 2000

Mar.

TABLE I of Liponyssus

_. -

100 46 100 53 1000 75 400 50 300 Died 500 1000 Died 5000 5000

May

on Chickens

.- - -

50 80 400 50 7000 50 500 25 300 50 500 800 2000 5000 5000

Apr.

sylviarum

I

3000

5000 Died

.

500

600 Died

. . -

40 12 250 18 SO0 50 100 100 300

July

65 35 200 45 300 50 300 35 500

June

-

. .

-

700

100

38 35 100 34 Died 46 65 44 400

Aug.

-

400

500

23 34 80 200

45 27 150 10

Sept.

_ -

2 g

x E

POULTRY

Temperatures Month November 1961 December January 1962 February March .4pril May June July August September

MITE

TABLE II in the Red Mite Hut Maximum (“0

Minimum (“0

14.4 14.4 10 14.4 17.7 27.7 22.2 32.7 28.8 30.5 32.2

- 3.0 -10.0 - 7.5 - 8.0 - 8.0 - 1.0 - 1.0 0 0 1.6 2.8

significant that the longest survivals were recorded in the natural temperatures of the chicken hut. Liponyssus The Liponyssus in tubes were examined every week, and although several mites survived for 14 days and a few for 21 days, they had all died within 28 days.

FIG. 3.

363

LONGEVITY

The numbers of Liponyssus present on the birds throughout the year are recorded in Table I. At least a few mites which had recently engorged were seen on the birds whenever they were examined. Liponyssus mites sometimes leave the birds, and although none could be found in the hut itself during the first few months of the experiment, severa were seen on the walls and ceiling from December onward. DISCUSSION

Under the conditions of these observations Dermanyssus survived without a blood meal for 34 weeks. Previous estimates of the survival of Dermanyssus without a blood meal vary greatly, ranging from 2 to 5 months. Many of the observations were made under unspecified conditions, and the majority of the text book references is probably derived from the original work of Wood (1917). More recently, however, Harrison (1962) observed

Grooved perch full of red mites.

All

Total

stages at

Protonymphs

Deutonymphs

Adults

89

Protonymphs

452

279 84

Adults Deutonymphs

Total

142 194

116

10°C Room

temperature Hut

35

20

Hut

34

10°C Room temperature

20 54

10

10°C Room

temperature Hut

87

120

69

72

62 85

59 65

85

55

74

79

90 80

100

60

46

86

72

Hut

2

used

Room temperature

10°C

Stored at

Number mites

-,“--

4

42

30

42 58

60

15

47

55

14

32

30 74

30

55

11

56

The Survival

21

26

-_“I--

30

27 48

32 45

33

5 55

18

28 6 57

11 45

14

18

26

4S

5 72

5 72

0

2 48

2

21

32

53

8

6

of Dermanyssus

29

19

27 48

5 54

18

35

11

18

5 72

48

2

21

10

23

11

19 48

2 48

7

35

0

9

5 72

39

2

7

12

TABLE gallinae Kept

23

11

19 48

2 47

7

35

9

5 72

38

2

7

14

-

19

6

17 38

2 41

3

30

0

5 57

36

2

4

16

Per cent mites

._

17

6

13 38

1 37

3

30

5 57

28

0

4

18

_

alive

_

13

6

12 21

1 28

2

25

5 31

27

3

20

_.

8

4

6 19

1 18

0

20

5 28

13

0

22

-

4

.

.

-

3.3

1.1

2 11

3 12 1.1

1 7

5

5 15

4

26

1 9

5

5 17

6

24

a Blood Meal

at weeks

in Glass Tubes without

III

.

.I

2

1.4 5 1.1

0 5

5

0 7

3

28

-

0.4

0.3 1.2 0

1

0

2

1

30

,...

..l

0.4

0.3 1.2

1

2

1

32

-

0.2

0.3 0

1

1

34

,,-_-

0

0

0

0

36

I

POULTRY

MITE

that under experimental conditions at 25°C and 80% relative humidity, adult mites could survive without food for 9 months. The ability of mites to withstand starvation is clearly of practical importance. Wood (1917) suggested that mites could be starved out of a building by leaving it empty for 4-5 months, but the present results which agree with Harrison’s (1962) estimates, indicate that a 5 months evacuation would be quite inadequate to ensure the elimination of the mites. The present experiment indicates that a period of more than 9 months is necessary. Infestations of Dermanyssus are not now as common as in former years. This is probably due to modern methods of housing poultry and to the quicker turnover of birds, especially in the broiler industry. Furthermore, the temperature of the poultry house is frequently controlled so that seasonal fluctuations in mite populations will not occur. The farmer is thus not likely to be caught unawares by a sudden increase in the activity of the mites due to a sudden rise in temperature. Nevertheless outbreaks still occur and because heavy infestations can severely affect even adult birds it is necessary to maintain a careful watch for mites, particularly in the summer when birds are kept in the same hut throughout the year. Herms (1953) advised that newly acquired birds should be kept in quarantine for 2 or 3 days so that mite infestations could be detected. It is suggested that a trap perch, similar to the type described in this paper, fitted into the quarantine shed, would aid the detection of any Dermanyssus present. The observation also suggest that the trap perch could be used as a means of control. Apparently all the mites prefer to remain in the perch, since none was found elsewhere in the shed. It therefore seems likely that if a suitable insecticide were placed inside the perch, the majority of the mites would come into contact with it. By this means, exposure of the birds to toxic

365

LONGEVITY

insecticides would be reduced. This possible use of the perch is to be further explored. Liponyssus will not survive for long without a blood meal. Caesar (1923) kept mites alive in a glass bottle for 18 days and Cameron (1938) succeeded in keeping mites alive without a blood meal for only 11 days. In this experiment they lived for up to 21 days. The results of the longevity experiments and the fact that mites were observed on the birds throughout the year confirm the statement of Cameron (1938) that Liponyssus does not aestivate. It is remarkable that although all the birds were exposed to the same initial infection and were housed together all the time, some birds became more heavily infested than others. This agrees with the observation by Cameron (1938) that some birds may be heavily infested while others seem to remain free of parasites, although his observation that mites occasionally leave a bird almost as suddenly as they attack it, was not confirmed in the present experiment. It is therefore very important to examine several birds when looking for an infestation of Liponyssus, as although the infestation must remain on at least some of the birds throughout the year, others may well be free of mites. REFERENCES

L. 1923. The feather mite-a new pest of poultry. Annual Report of the Entomological Society of Ontario 63, 47-48. CAMERON, D. 1938. The Northern fowl mite (Liponyssus sylviarum C & F 1877). Investigations at Macdonald College, Quebec, with a summary of previous work. Canadian Journal of Research 16, 230-254. CHAMBERLAIN, R. W., AND SIKES, R. K.-1950. Laboratory rearing methods for three common species of bird mites. Journal of Parasitology 36, 461465. EDGAR, S. A., WALSH, W. L., AND JOHNSON, L. W. 1949. Comparative efficacy of several insecticides and methods of application in the control of lice on chickens. Poultry Science 28, 320-338. HARRISON, I. R. 1960. The control of the poultry red mite with l-naphthyl-N-methyl-carbamate. Veterinary Record 72, 298-300.

CAESAR,

366

KIRKWOOD

HARRISON, I. R. 1962. The biology of poultry red mite (Dermanyssus gallinae) and its control with contact and systemic insecticides. Proceedings of Xlth International Entomological Congress, Vienna 1960 469-473. HARSHBARCER, J. C., AND RAFFENSPERGER, E. M. 1961. An evaluation of coding systems for estimating populations of the shaft louse Menopon

gallinae. 74-76.

Journal

of Economic

HERMS, W. B. 1953. “Medical millan, New York.

Entomology

Entomology.”

54, Mac-

WOOD, H. P. 1917. The chicken mite: its life history and habits. United States Department of Agriculture, Bulletin No. 5.53.