A STUDY OF WEIL-FELIX REACTION IN THE DIAGNOSIS OF TYPHUS

FEVER IN BOMBAY*

By D. W. SOMAN

Haffkine Institute, Bombay

.The demonstration of causal rickettsia for

early diagnosis of typhus fever is a time-consum- ing procedure and requires the use of a com- plicated technique as yolk-sac cultivation or

inoculation of different laboratory animals. Sero- logical tests such as the Weil-Felix reaction, com- plement fixation or rickettsial agglutination are much simpler to perform but the last two of these require specific rickettsial antigens; the prepara- tion of these is not within the scope of an

average small laboratory, so a laboratory worker has to continue to rely on the Weil- Felix reaction. Three serological varieties of B. proteus X, known as proteus X19, X2 and XK, are the only reagents by means of which the diagnosis of different varieties of typhus can be made.

As with many serological tests, the study of Weil-Felix reaction has brought to light certain anomalies and limitations that were not at first realized. Many workers have come to doubt its specificity on account of the reaction being posi- tive during the course of other diseases. Factors such as standardization of technique, endemicity of infection, agglutinin level of local population, have to be reckoned with in the correct inter-

pretation of this reaction. It is the purpose of this article to study the Weil-Felix reaction done on a large number of sera from pyrexial and apyrexial cases and to see how far some of

* This work has been carried out under the auspices of the Indian Research Fund Association.

650 THE INDIAN MEDICAL GAZETTE [Nov., 1947

the factors mentioned above interfere with the

proper interpretation in the correct diagnosis of typhus fever.

Material and Method To study the level of proteus OX agglutinins

in the Bombay population, 500 sera sent for Wassermann test and 763 sera sent for Widal tests were tested for Weil-Felix reaction by the method described below. In testing sera for the Widal reaction, the combined method of clot culture and the Widal reaction (Soman, 1932, 1934) was used, so that 185 sera from bacterio- logically proved typhoid and para-typhoid cases were available for study. Fresh alcoholic proteus suspensions were prepared from the three standard proteus strains every three months

according to the method of Bridges (1944) and the Felix's (1944) technique was slightly modified. The tests were incubated at 50 to

52?C. instead of at 37?C. in the water-bath for four hours and kept overnight in the ice- chest for the final reading. Whenever a

serum obtained from a pyrexial case showed a titre of 1 : 50 or 1 : 125 a repeat specimen was requested with a brief note on clinical

history. Results of the Weil-Felix reaction on sera coming from pyrexial and apyrexial cases are summarized in tables I and II. Results of the same test on 185 samples of sera from typhoid and para-typhoid cases are summarized in table III, while the results obtained in 28 cases of clinically diagnosed typhus fever are shown in tables IV and V. Clinical history was

available in 13 cases. In 9 cases of 0X19 type, male guinea-pigs were inoculated intraperito- neally with 5 c.c. of patients' blood and in 3 cases of OXK type mice were similarly inoculated with 0.5 c.c. of blood.

Table I

Results of Weil-Felix reaction on 500 sera sent for WR

Titre of serum

Below 25 25 50 100 200

Suspensions op B. proteus

OX19

489 7 1 3

OX2

500 0 0 0

0 i 0

500 500

OXK

499 0 1 0 0

500

It is known that sera from normal persons

may contain low titre proteus OX agglutinins even in areas free from typhus infection. The results in table I showed only 3 sera out of 500 positive for proteus OX19 agglutinins in 1 : 100 dilution. Tables I and II, when considered together, showed that out of 1,263 sera examined, only 23 samples were positive in dilutions rang- ing from 1 : 50 to 1 : 125, giving a percentage

Table II

Results of Weil-Felix reaction on 763 sera from febrile cases including typhus cases

Titre of serum

Below 50 50 125 250 500 or over

Suspensions op B. proteus

OX19

714 5 6 10 28

763

OX2

759 2 2 0 0

763

OXK

759 2 1 0 1

763

of 1.8; ten sera were positive in a dilution of 1 : 250 and 29 in a dilution of 1 : 500 or over. With the exclusion of those showing a titre of 1: 250 or over, a very large number of sera was either negative or below a titre of 1: 50. Weil (1920) in a series of 1,837 control sera from febrile and afebrile cases recorded only 1.2 per cent agglutinating the strain of proteus OX19 in 1 : 50 dilution; this titre according to Felix

(1944) would have to be doubled to bring it on line with the results obtained by the use of alcoholic suspensions. A minimum diagnostic titre of 1 : 100 or 1 : 200 for typhus infection in non-endemic areas was suggested by many workers as MacKenzie (1941), McConn (1943) and Felix (1944). But Baker and others

(1943), Brockbank and Whittaker (1944), Dyer (1944) and Dick (1946) did not feel justified in considering any titres below 1 : 480 as diagnostic of typhus infection. In the present series, as

98.2 per cent sera were found to be negative in a titre of 1 : 125, this titre could safely be taken as the minimum diagnostic titre for typhus in- fection in the presence of suggestive clinical history.

In order to study the problem of non-specific rise in Weil-Felix titres, 174 cases of typhoid and 11 of para-typhoid A infection were studied in relation to their Weil-Felix titres at different

stages of disease.

Table III

Results of Weil-Felix reaction in 185 typhoid and para-typhoid cases

Titre of serum

Below 50 50 125 250

Suspensions of B. proteus

OX19 OX2 OXK

183 184 184 1 1 1 0 0 0 1 0 0

185 185 185

Nov., 1947] WEIL-FELIX -REACTION IN TYPHUS : SOMAN 651

Only one serum showed a 'titre of 1 : 250. This finding is of special interest in view of the confusing reference in the literature to the '

anamnestic rise in titre' due to non-specific infection and clearly showed that in the diagnosis of typhus infection, non-specific rise in titre due to enteric infection did not occur. Felix (1944), who investigated this possibility of non-

specific rise in 0X19 titres, observed for

periods of several weeks typhoid, pneumonia and other febrile cases with and without history of previous typhus infection and concluded that even those patients who showed normal or

residual agglutinins in titres ranging from 1 : 50 to 1 : 200 showed no re-stimulation of these

agglutinins. The findings in the present series, therefore, appear to be in complete accord with those of Felix and are very significant because enteric fever figures so prominently in the differential diagnosis of typhus fever. A high residual OX19 titre may rarely lead to

some difficulty in arriving at correct diagnosis necessitating repeat observations. Following is a ease in point observed by the author :? A sample of blood tested for Widal on the 17th

day of illness showed typhoid 0 and H titres of 1 : 250 and Weil-Felix 0X19 titre of 1 : 1,000. An enquiry into the clinical history of the case did not reveal any presence of rash or history of T.A.B. inoculation or previous typhus infection.

A repeat specimen later showed a rise in typhoid 0 and H titre of 1 : 500 with the Weil-Felix 0X19 titre stationary. The clot culture was sterile twice. The subsequent rise in Widal titre, with the Weil-Felix titre unchanged, distinctly pointed to the true nature of infection which was subsequently confirmed by isolation of B. typhosus from the patients' stool. The Weil-Felix titre in 28 cases of typhus

infection was studied with many repeat observa- tions. Serologically, 23 cases were of the 0X19 type, 2 of 0X2 type and 3 of OXK type. The results of these cases fall into two groups.

One group in which titres rose very high early iibove the diagnostic level (table IV) and the

other in which they did not rise beyond 1 : 500

even during the third week of illness (table V). The possibility of such cases with low-titre

reactions had to be kept in mind otherwise they were likely to be missed or wrongly interpreted. Frequent repeat observations to demonstrate rise in titre or the causal virus was the only method of arriving at correct diagnosis. Clinical

history was available in 13 out of 28 cases. The infection was of a mild nature and showed many clinical features in common. The pyrexia was of a remittent or intermittent type lasting from 14 to 16 days, terminating by lysis within 2 to 3 days. Slow pulse, persistent headache and moderate leukocytosis were prominent features.

Table IV

Results of Weil-Felix reaction in 12 cases of typhus showing low titre

Serial number

I

II

III

IV

VI

VII VIII IX X XI XII XIII

XIV

Widal number

319 366 337 370 529

560

589

553 598 596 619 687 699 390 433 462 583 613 616 1426 1427 1494 1193 1211 1241

Widal titre

125 (para B) 125 ( ? ) Negative

50 (TYH) 125 (para B)

125 (TYO) 125 (para B) 125 (TYO) 125 (para B) Negative

Weil-Felix tithe

0X19 I 0X2

500

v 2,500

2,500 [ 2,500 1,000 j 250 125 50 125

250

2,500- 1,250 250

1,250 125

1,250 1,250 125 2,500 125

1,250 125

1,250 1,250 1,250

250 500 500

OXK

125

500 1,250 500

Day of fever

13 29 13 20 5

12

15 24 8 13 14 18 14 23 12 13 7 7 12 14 32 13 14 22

Result of animal inoculation

N.D.

Negative.

Febrile reaction. Neill-Mooser reaction. R. mooseri -f.

N.D.

Febrile reaction.

ND.

N.D. N.D. N.D. N.D. N.D. Febrile reaction. Negative.

R. orientalis -f.

N.D. = Animal inoculation not done.

652 THE INDIAN MEDICAL GAZETTE ? [Nov., 1947

Table V

Results of Weil-Felix reaction in 14 coses oj typhus showing low titre

Serial Widal , ...

number number Wldal tltre

I 378 Negative 450

II 451 499

III 624 639 50 (para B) 701 125 (para B)

IV 631 Negative 648 635 688

724 VI 677

700 742

VII 909 QQl

VIII 351 IX 449 X 315 XI 752 XII 1555 XIII 1267 XIV 1325

Weil-Felix titre

0X19

50 250 50

500

250 500 500 125 500

Negative 500 250 250 125 500 125

125 (para B) 500 50 (para B) 500 Negative 500

500 500 500

0X2 OXK

60 125

250 125 125

125 50

50

125 250

125 500

Day of fever

12 14 21 5 10 10 17 20 27 8 13 20 12 20 12 12 13 19

ie 12

Result of animal inoculation

7 Negative. 14 10 Febrile reaction. 21 Neill-Mooser reaction.

R. mooseri +. N.D.

Febrile reaction.

N.D.

N.D.

N.D.

N.D. Febrile reaction. N.D. NJ>. N.D. R. orientalis +. R. orientalis +?

N.D. = Animal inoculation not done.

Rash was present in 4 out of 12 cases. Inocula- tion of patients' blood in male guinea-pig elicited febrile reaction in 6 cases out of 9.

Only in 2 cases guinea-pigs showed pyrexia and typical Neill-Mooser reaction and Rickettsia mooseri were demonstrated in smears from the tunica exudate (table IV, no. 3 and table

V, no. 2). Mice were inoculated intraperito- neally with blood from OXK type of cases and R. orientalis were successfully demostrated in

peritoneal exudate (table IV, no. 14 and table

V, nos. 13 and 14). In 8 out of 13 cases of typhus fever

reported by Patel (1943a) and Patel (1943b) in

Bombay, Weil-Felix titre did not rise higher than 1 : 500 even between 9th and 17th day of diseases, van den Ende and others (1943) in 12 cases of murine typhus in previously immunized persons with typhus vaccines observed that the disease assumed a mild form and the Weil-Felix titre did not rise higher than J. : 500. Such observa- tions and especially those reported from

Bombay lend significant support to the author's findings in this article of 14 cases of typhus fever with low-titre reactions.

Conclusions

Typhus, as it occurs in Bombay, is chiefly flea-borne 0X19 in type. Cases seen are pre- dominantly mild, with or without rash, simulat- ing other mild infections of enteric fever. The

laboratory records of typhus cases in Bombay

do not represent the total incidence of this disease. Cases also occur in which 0X19 titres

may rise very high or remain low throughout the course of the disease. It is shown that the titre of 1 : 125 in the early stage of the disease can be taken as suggestive only when considered in relation to clinical history, while titres of 1 : 250 or higher as diagnostic of typhus infection. The low-titre reactions require, however, to be confirmed by repeat examinations to demon- strate rise in titre in all cases. Typhoid and para-typhoid infections do not influence Weil- Felix titres and do not give rise to anamnestic reactions and it is also true vice versa. Typhus cases of flea-borne variety may show both 0X19 and 0X2 titres but the 0X2 titre is usually lower than 0X19 titre. Ordinarily, 0X19 titre does not differentiate epidemic or louse-borne infection from the endemic or flea-borne type, which can only be proved by doing complement- fixation tests. Typhus cases showing low Weil- Felix titres against B. proteus 0X19 and high titre against B. proteus X2 or showing high 0X2 titres only against B. proteus X2 (table IV, no. 13 and table V, no. 12) are probably cases of tick typhus reported by Megaw (1921) in India or cases allied to Rocky Mountain Spotted fever group of America, transmitted through ticks; the aetiology of this group remains yet to be worked out for India. Typhus cases OXK in type, which is a mite-borne infection, do occur in Bombay, but the number is proportionately

Nov., 1947] INSULIN SENSITIVITY;: GUPTA & HAMEED 653

small. Significant titres against B. proteus OXK strains occur in relapsing fever (Robinson, 1942; Elsdon-Dew, 1943) which may cause errors in

diagnosis. But no such cases have been observed in Bombay during the last twenty years.

Typhus cases in which Weil-Felix reactions may remain completely negative throughout the course of the disease are reported in northern Australia and North America known as

'

Q' fever. No such cases are reported 'in India so far. In India, correct data are not available as to the mode of transmission of rickettsial infection from one person to another, because the arthropod vectors and the reservoirs of infec- tion have not yet been thoroughly determined. In spite of all these limitations and those dis- cussed above, Weil-Felix reaction, though a

non-specific agglutination test, appears quite diagnostic in at least three known varieties of typhus and should be carried out on every case of continued and irregular pyrexia, mild or

severe, with or without rash, taking due care to exclude the diagnosis of enteric infection and certain other non-specific conditions discussed above.

Summary 1. Weil-Felix tests were carried out on 1,263

sera from pyrexial and apyrexial cases and a

titre of 1 : 125 was shown to be presumptive of diagnosis of typhus infection in a pyrexial case with suggestive clinical history; a titre of 1 : 250 or over was considered as confirmatory of the disease.

2. 185 sera from proved cases of typhoid and para-tyhoid infection were studied in relation to their Weil-Felix titres. The titres recorded were always below 1 : 250 except in one case in which Weil-Felix titre of 1 : 1,000 was observed.

3. The study of Weil-Felix titres in 28 cases of typhus' fever showed that high- and low-

titre reactions frequently occurred. In cases

-especially with low-titre reactions, repeated examinations for rise in titre were necessary to arrive at a correct diagnosis.

4. The problem of typhus, as it occurs in

Bombay, is discussed with the role of Weil-Felix test in its diagnosis and its limitations stressed in the interpretation of results.

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